Background: Prospective studies have shown that C-reactive protein (CRP) is a predictor of hypertension. Because of confounding variables, a causal linkage between CRP and hypertension has not been clearly shown. We investigated whether high circulating concentrations of human CRP can induce hypertension in rats.
Methods: We administered a single intravenous injection of adeno-associated virus-green fluorescent protein (AAV-GFP) or AAV-hCRP and measured blood pressure. Using ELISA, we measured serum hCRP, serum endothelin 1 (ET-1), and urine cGMP, and we measured serum nitric oxide (NO) using the Griess method. We recorded heart rate, maximum pressure, arterial elastance, mean aortic pressure, cardiac output, and maximum rate of rise in left ventricular pressure (dP/dt max).
Results: A single injection of AAV-hCRP resulted in efficient and sustained hCRP expression and led to increased blood pressure 2 months after gene transfer that persisted for another 2 months. This effect was associated with decreased NO production, as demonstrated by decreased serum NO concentration and urinary cGMP excretion, and impairment of endothelial-dependent vascular relaxation. CRP transduction also increased expression of angiotensin type 1 receptor, ET-1, and endothelin type A receptor, decreased expression of angiotensin type 2 receptor and endothelial NO synthase in thoracic aortas, and increased arterial stiffness. Ex vivo studies indicated a similar detrimental effect of CRP that was reversed by the NO donor.
Conclusion: AAV vector-mediated CRP expression resulted in hypertension mediated through reduced NO production and subsequent alteration in ET-1 and renin-angiotensin system activation. Impaired arterial elasticity may also contribute to CRP-induced hypertension. These results support a causal role for CRP in the pathogenesis of hypertension.