STAT3 Contributes to Intracranial Aneurysm Formation and Rupture by Modulating Inflammatory Response

Abstract

Intracranial aneurysm (IA) is a common type of refractory cerebrovascular diseases. Inflammatory responses have been reported to be associated with the pathogenesis of IA. We aimed to study the role of STAT3 on IA formation and inflammatory response. STAT3 expression and clinicopathological factors were analyzed in IA and normal cerebral arteries. mRNA level of STAT3 was detected in normal, unruptured, and ruptured IA tissues by RT-PCR and Western blot. Inflammatory cytokines were examined by ELISA in unruptured, ruptured IA tissues, as well as cells with STAT3 overexpression or knockdown. mRNA of phenotypic modulation-related factors was tested by RT-PCR in STAT3 overexpressing or knockdown VSMCs. STAT3 expression was upregulated in ruptured IA tissues and highly associated with IA diameter and IA type. Inflammatory cytokine secretion was increased in ruptured IA samples and positively correlated with STAT3 expression. STAT3 overexpression led to enhanced expression of SM-α actin, SM-MHC, MMP2, and MMP9, and increased secretion of inflammatory cytokines. Our findings have demonstrated that STAT3 is a key regulator in IA formation by modulating inflammatory cytokine expression.

Keywords: Inflammatory response; Intracranial aneurysms; STAT3; Vascular smooth muscle cell.

Fig. 1

Upregulation of STAT3 in unruptured and ruptured intracranial aneurysm tissues. a qRT-PCR was used to measure the STAT3 mRNA expressions among normal vascular tissues (n = 43), unruptured intracranial aneurysm tissues (n = 32), and ruptured intracranial aneurysm tissues (n = 50). The expressions were normalized to normal group. Box plot with all data points was used to present the data. b Representative blots of STAT3 protein among different groups and quantification among normal vascular tissues (n = 43), unruptured intracranial aneurysm tissues (n = 32), and ruptured intracranial aneurysm tissues (n = 50). Data were presented as mean ± SD. **p < 0.01, ***p < 0.001 between the indicated groups

Fig. 2

Inflammatory response in unruptured and ruptured intracranial aneurysm tissues. Levels of MCP-1 (a) TNF-α, (b), IL-1β, (c), and IL-6 (d) are increased in unruptured intracranial aneurysm tissues (n = 32) and ruptured intracranial aneurysm tissues (n = 50) compared to normal vascular tissues (n = 43). Box plot with all data points was used to presented the data. **p < 0.01, ***p < 0.001

Fig. 3

Correlation of STAT3 expression with inflammatory response in intracranial aneurysm tissues. Pearson’s correlation analysis was carried out to measure the r of STAT3 expression with the concentrations of MCP-1 (a), TNF-α (b), IL-1β (c), and IL-6 (d)

Fig. 4

Transfection efficiency of pcDNA-STAT3 and si-STAT3 in vascular smooth muscle cells (VSMCs) was validated via qRT-PCR (a, c) and Western blot assays (b, d). Data were presented as mean ± SD. ***p < 0.001

Fig. 5

The effects of STAT3 on vascular smooth muscle cells (VSMCs) phenotypic modulation. qRT-PCR was used to measure the mRNA expressions of SM-MHC (a), SM-α actin (b), MMP2 (c), and MMP9 (d). Data were presented as mean ± SD. *p < 0.05, **p < 0.01

Fig. 6

The effects of STAT3 on vascular smooth muscle cells (VSMCs) inflammatory response modulation. ELISA was used to measure the levels of MCP-1 (a), TNF-α (b), IL-1β (c), and IL-6 (d). qRT-PCR was used to measure the mRNA expressions of MCP-1 (e), TNF-α (f), IL-1β (g), and IL-6 (h). Data were shown as mean ± SD. *p < 0.05, **p < 0.01