Increased expression of cytokines in a new traumatic model of abdominal aortic aneurysms associated with hypercholesterolemic diet in Wistar rats
Authors: Mata Karina M , Fernandes Cleverson R , Tefe‐Silva Cristiane , Floriano Elaine M , Ramos Simone G 
Published: November 2023

Abdominal aortic aneurysm (AAA) is a chronic degenerative disease reaching high morbidity and mortality levels. Weakening of aortic wall and dilatation up 50% are the mainly characteristics of AAA, associated with atherosclerosis and increase of proinflammatory cytokines. Was developed in our laboratory a new traumatic model of abdominal aortic aneurysm (AAA) through the combination of two potential causes of metalloproteinases secretion and activation – acute inflammation and blood flow turbulence. In isolation, these causes were insufficient to provoke arterial dilatation and aneurysms. However, when combined, due to inflammatory processes and abundant MMP‐2 and MMP‐9 secretion, there was elastin degradation, wall remodelling and aneurysm formation. The objective of this study was investigate the role of cytokines in this new traumatic model of abdominal aortic aneurysms associated with hypercholesterolemic diet.

Methods

Forty‐eight male wistar rats were divided into four groups: Control Standard Diet (CSd), Control hypercholesterolemic diet (CHd), Aneurysm Standard Diet (ASd), Aneurysm hypercholesterolemic diet (AHd), and were euthanized in 7 and 30 days post‐surgery. Hypercholesterolemia was induced in rats feeding a standard diet supplemented with 4% cholesterol, 1% cholic acid, and 0.5% 2‐thiouracil. This hypercholesterolemic diet started to be offered 2 days before surgery. The animals submitted to surgery induction of abdominal aortic aneurysms consumed the hypercholesterolemic diet for more 7 and 30 days. At 7 and 30 days post surgery the animals were euthanized, and the aortas were collected for morphological analyses, immunohistochemistry, Elisa and Western Blot for cytokines analysis [interleukin 6 (IL‐6), Tumor necrosis factor alpha (TNF‐alpha), transforming growth factor beta (TGF‐beta) and Monocyte Chemoattractant Protein‐1 (MCP‐1)]. The animal protocols were approved by Committee on Animal Research of Ribeirão Preto Medical School of University of São Paulo and the animals were handled according to the guiding principles described in the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

Results

The AAAs developed in this experimental model show an extraordinary aortic dilatation ratio with similar morphology to human abdominal aneurysms in just 7 days in approximately 65% of the animals. Macroscopic differences were no observed between Aneurysm Standard Diet (ASd) and in Aneurysm hypercholesterolemic diet (AHd). Beyond the elastic fiber destruction, deposition of collagen and intense remodeling process characterized by a severe inflammatory response, these alterations were directly related to the dramatic expressions increase of the IL‐6, TNF‐alpha, TGF‐beta and MCP‐1 in Aneurysm Standard Diet (ASd) and in Aneurysm hypercholesterolemic diet (AHd) compared to controls groups (CSd and CHd); P<0.05. In the Control hypercholesterolemic diet (CHd) was observed a slight increase compared to control group (CSd) P<0.05.

Conclusion

These results suggest that the IL‐6, TNF‐alpha, TGF‐beta and MCP‐1 may play a crucial and an important role in the development and progression in both aneurysms and atherosclerosis diseases. Moreover, this rat model has great potential for improving the understanding of the etiopathogenesis of AAA, as well as for investigating new therapeutic treatments.

Support or Funding Information

This study was supported by grants of FAPESP and CNPq.