Short- and Long-Term Treatment of Mouse Cortical Primary Astrocytes with β-Amyloid Differentially Regulates the mRNA Expression of L-Type Calcium Channels

Abstract

Background: It is well established that reactive astrocytes express L-type calcium channels (LTCC), but their functional role is completely unknown. We have recently shown that reactive astrocytes highly express the Ca_V1.2 α₁-subunit around β-amyloid (Aβ) plaques in an Alzheimer mouse model. The aim of the present study was to explore whether Aβ peptides may regulate the mRNA expression of all LTCC subunits in primary mouse astrocytes in culture. Methods: Confluent primary astrocytes were incubated with 10 µg/ml of human or murine Aβ or the toxic fragment Aβ_25-35 for 3 days or for 3 weeks. The LTCC subunits were determined by quantitative RT-PCR. Results: Our data show that murine Aβ₄₂ slightly but significantly increased Ca_V1.2 and Ca_V1.3 expression when incubated for 3 days. This acute treatment with murine Aβ enhanced β₂ and β₃ mRNA levels but decreased α₂δ-2 mRNA expression. When astrocytes were incubated for 3 weeks, the levels of Ca_V1.2 α₁ were significantly decreased by the murine Aβ and the toxic fragment. As a control, the protein kinase C-ε activator DCP-LA displayed a decrease in Ca_V2.1 expression. Conclusion: In conclusion, our data show that Aβ can differentially regulate LTCC expression in primary mouse astrocytes depending on incubation time.

The L-type calcium channel Cav1.3 is required for proper hippocampal neurogenesis and cognitive functions

“…A subset of astrocytes in the hippocampus indeed expresses Cav1.3 (Fig. 2g) [46,59], and upregulation of Cav1.3 has been demonstrated in reactive astrocytes of the mouse hippocampus after pilocarpine-induced status epilepticus [60]. Thus, Cav1.3 may contribute to volume regulation and modulation of the activity state of astrocytes in the hippocampus and could be involved in astrogliosis in chronic neurodegenerative disorders such as Alzheimer´s disease or in acute CNS lesions such as spinal cord injury.…”

Astroglia in Alzheimer’s Disease

“…These studies did not, however, discriminate between cell types. Many other components of Ca 2+ signalling system are affected by AD; these include components calpain-10 [85], NFAT (Nuclear factor of activated T-cells) [1], NF-κB [93], calcineurin [93,199], L-type calcium channels [59] and store-operated Ca 2+ channels [239]. All in all 32 genes associated with Ca 2+ signalling were found to be affected in the transcriptome of astrocytes microdissected from patients with different Braak stages of AD.…”

Ca2+homeostasis dysregulation in Alzheimer's disease: a focus on plasma membrane and cell organelles

“…(K670M/N671L) mutations, and the overexpressed subunits were further found to cluster around Ab plaques (66). However, in the subsequent in vitro study on cortical astrocytes, it was revealed that acute (days) exposure to murine Ab42 increased the expression of Ca v 1.2 a1-subunit, whereas chronic (weeks) treatment decreased it (67). As the results suggest, it may not only be the Ab peptides but also the overall impact from Ab plaques that stimulate the expression of L-type VGCC in reactive astrocytes (67).…”

“…However, in the subsequent in vitro study on cortical astrocytes, it was revealed that acute (days) exposure to murine Ab42 increased the expression of Ca v 1.2 a1-subunit, whereas chronic (weeks) treatment decreased it (67). As the results suggest, it may not only be the Ab peptides but also the overall impact from Ab plaques that stimulate the expression of L-type VGCC in reactive astrocytes (67). Further, Ab23-35 exposure increases the surface protein level of Ca v 1.2 and Ca v 1.3 L-type VGCC in cultured hippocampal neurons, as well as enhancing Ca v 1.3 channel activity in HEK293 cells (68).…”