Intervention effect of regulating GABA-A receptor activity on the formation of experimental abdominal aortic aneurysm in rats

Abstract

Abdominal aortic aneurysm is a potentially fatal vascular inflammatory disease characterized by infiltration of various inflammatory cells.The GABA-A receptor is expressed in many inflammatory cells such as macrophages and T cells and has anti-inflammatory and antioxidant effects. Therefore, the GABA-A receptor may become a potential therapeutic target for abdominal aortic aneurysms. The purpose of this study was to investigate the effect of regulating the activity of the GABA-A receptor on the formation of experimental abdominal aortic aneurysm in rats. In this study, the abdominal aortic aneurysm model of rats was established by aorta intracavitary perfusion of elastase combined with aorta extracavitary infiltration of calcium chloride. GABA-A receptor agonist (topiramate) and antagonist (bicuculline) were used to treating the abdominal aortic aneurysm model rats, which were divided into sham operation group, model group, topiramate group, and bicuculline group(n = 10). Histopathology, immunohistochemistry, fluorescence quantitative PCR, Western blotting, ELISA and Gelatine zymogram were used to study. Regulation of GABA-A receptor activity can interfere with the development and severity of abdominal aortic aneurysms in rats. The GABA-A receptor agonist topiramate reduces the infiltration of inflammatory cells, particularly T cells, into the abdominal aortic wall, while also modulating the balance of Th1/Th2 cytokines in peripheral blood, leading to a significant reduction in inflammatory responses. Additionally, topiramate decreases the secretion of matrix metalloproteinases MMP2 and MMP9, thereby inhibiting extracellular matrix degradation and slowing the progression of aneurysms. In contrast, the GABA-A receptor antagonist bicuculline exacerbates inflammation and promotes aneurysm development. At the molecular level, the mechanisms of action of the GABA-A receptor agonist topiramate and the antagonist bicuculline may involve inhibition or activation of the p38 MAPK signaling pathway. Regulation of GABA-A receptor activity can effectively intervene in the occurrence and development of abdominal aortic aneurysms in rats.

Keywords: Abdominal aortic aneurysm; Bicuculline; GABA; GABA-A receptor; Topiramate.

Fig. 1

Dilatation degree of abdominal aorta and appearance of aneurysm in each group. (A) No dilation was observed in the perfused segment of the abdominal aorta in the Sham group. (B) Localized saccular aneurysm formation was observed in the perfused segment of the abdominal aorta in the Model group. (C) Localized mild dilation was observed in the perfused segment of the abdominal aorta in the Topiramate group. (D) Irregular aneurysm formation was observed in the perfused segment of the abdominal aorta in the Bicuculline group.

Fig. 2

Histopathological changes of abdominal aorta of rats in each group. (A) The vascular wall structure in the Sham group remains intact. (B) In the Model group, the vessel wall is thinned, with discontinuous, partially lost or fragmented elastic and collagen fibers, and a reduction in smooth muscle cells. (C) In the Topiramate group, the vessel wall is partially thinned, but clear inner and outer elastic layers are still visible, and smooth muscle cells are arranged in an orderly fashion. (D) In the Bicuculline group, the vessel wall is significantly thinned, with degradation of the extracellular matrix, smooth muscle cell loss, and dissection formation. (E) Quantitative analysis of normalized vascular wall thickness. (F) Differences in vascular wall thickness across individual rats.

Fig. 3

Infiltration of inflammatory cells in abdominal aorta wall of rats in each. (A-C). Representative pictures of IHC staining for CD68, CD3, and CD20 cells. (D) Analysis of cell counts for CD68, CD3, and CD20. Comparison with the Model group: *P < 0.05, **P < 0.01; n=10. ACS, aortic cross section.

Fig. 4

Expression of GABA α5 subunit in inflammatory cells in the abdominal aortic wall across different groups. (A) Widespread expression of the GABA α5 subunit in infiltrating inflammatory cells in the Model, Topiramate, and Bicuculline groups. (B) Quantitative analysis of GABA α5 subunit-positive inflammatory cells, *P < 0.05 compared to the Model group, n = 10. ACS, aortic cross section. (C) Representative immunofluorescence images showing colocalization of CD3 and GABA α5 subunit.

Fig. 5

Phosphorylation levels of the p38 MAPK signaling pathway and expression and activity of MMP2/MMP9 in the abdominal aortic wall. (A) Representative Western blot bands showing expression of p38, P-p38, MMP2, and MMP9 proteins in each group. (B) Representative zymography images of MMP2 and MMP9 enzyme activities in each group. (C) Relative quantitative analysis of MMP2 and MMP9 mRNA expression; n = 6. (D) Relative quantitative analysis of MMP2 and MMP9 protein expression; n = 4. (E) Quantitative analysis of MMP2 and MMP9 protein activity; n = 4. (F) Relative quantitative analysis of p38 and P-p38 protein expression; n = 4. *P < 0.05, **P < 0.01 compared to the Model group.To present the data clearly and concisely, gels/blots were cropped. Uncropped original gels/blots are shown in Supplementary Figures S1-S2.