Cold Inducible RNA-Binding Protein Promotes the Development of Alzheimer's Disease Partly by Inhibition of uPA in Astrocytes

Background: Cold inducible RNA-binding protein (CIRP) is an important danger-associated molecular pattern involved in tissue-specific and systemic inflammation related to inflammation and Alzheimer's disease (AD). However, the precise roles and mechanism of CIRP in the functional changes in astrocytes during the development of AD are still unknown. This study aimed to assess gene expression alterations in astrocytes after they overexpress CIRP (oe-CIRP) and to explore the relationship between abnormal CIRP expression and AD.

Methods: We created astrocyte cell lines with a CIRP or control vector expression using three human glioma cell lines U87, U251 and H4, and analyzed the mRNA expression profiles of 3 pairs of cells via microarray. Bioinformatics identified differentially expressed mRNAs between CIRP-overexpressing (ov-CIRP) and control groups, validated by q-PCR and Western blotting (WB). Finally, the effect of CIRP overexpression in astrocytes on neurons was observed in a coculture system.

Results: We identified 119 mRNAs with obvious fold changes between the ov-CIRP and control groups for all 3 pairs of human glioma cell lines. The biological functional analysis indicated that urokinase plasminogen activator (uPA), a gene whose expression significantly decreased after CIRP overexpression, was closely associated with AD. WB and q-PCR confirmed that CIRP overexpression significantly inhibited uPA at both mRNA and protein levels in U87, U251 and H4 cells. Moreover, compared with those cocultured with control astrocytes, SH-SY5Y cells cocultured with CIRP-overexpressing astrocytes exhibited a significant increase in the expression of amyloid-β (Aβ)1-42 and the hyperphosphorylated microtubule-associated protein tau (Tau).

Conclusion: CIRP overexpression in astrocytes inhibits uPA expression, promoting Aβ1-42 production and tau phosphorylation in neurons, thereby increasing AD risk. These results suggest that the overexpression of CIRP in astrocytes contributes to the development of AD.