Transgenic human C-reactive protein affects oxidative stress but not inflammation biomarkers in the aorta of spontaneously hypertensive rats

C-reactive protein (CRP) is an acute inflammatory protein detected in obese patients with metabolic syndrome. Moreover, increased CRP levels have been linked with atherosclerotic disease, congestive heart failure, and ischemic heart disease, suggesting that it is not only a biomarker but also plays an active role in the pathophysiology of cardiovascular diseases. Since endothelial dysfunction plays an essential role in various cardiovascular pathologies and is characterized by increased expression of cell adhesion molecules and inflammatory markers, we aimed to detect specific markers of endothelial dysfunction, inflammation, and oxidative stress in spontaneously hypertensive rats (SHR) expressing human CRP. This model is genetically predisposed to the development of the metabolic syndrome.

Transgenic SHR male rats (SHR-CRP) and non-transgenic SHR (SHR) at the age of 8 months were used. Metabolic profile (including serum and tissue triglyceride (TAG), serum insulin concentrations, insulin-stimulated incorporation of glucose, and serum non-esterified fatty acids (NEFA) levels) was measured. In addition, human serum CRP, MCP-1 (monocyte chemoattractant protein-1), and adiponectin were evaluated by means of ELISA, histological analysis was used to study morphological changes in the aorta, and western blot analysis of aortic tissue was performed to detect expression of endothelial, inflammatory, and oxidative stress markers.

The presence of human CRP was associated with significantly decreased insulin-stimulated glycogenesis in skeletal muscle, increased muscle and hepatic accumulation of TAG and decreased plasmatic cGMP concentrations, reduced adiponectin levels, and increased monocyte chemoattractant protein-1 (MCP-1) levels in the blood, suggesting pro-inflammatory and presence of multiple features of metabolic syndrome in SHR-CRP animals. Histological analysis of aortic sections did not reveal any visible morphological changes in animals from both SHR and SHR-CRP rats. Western blot analysis of the expression of proteins related to the proper function of endothelium demonstrated significant differences in the expression of p-eNOS/eNOS in the aorta, although endoglin (ENG) protein expression remained unaffected. In addition, the presence of human CRP in SHR in this study did not affect the expression of inflammatory markers, namely p-NFkB, P-selectin, and COX2 in the aorta. On the other hand, biomarkers related to oxidative stress, such as HO-1 and SOD3, were significantly changed, indicating the induction of oxidative stress.

Our findings demonstrate that CRP alone cannot fully induce the expression of endothelial dysfunction biomarkers, suggesting other risk factors of cardiovascular disorders are necessary to be involved to induce endothelial dysfunction with CRP.