There is evidence to suggest that hypertension involves a chronic low-grade systemic inflammatory response; however, the underlying mechanisms are unclear. To further understand the role of inflammation in hypertension, we used a rat renovascular model of hypertension in which we administered the TNF-α synthesis inhibitor pentoxifylline (PTX, 30 mg/kg/day) in the drinking water for 60 days. In conscious rats, PTX administration significantly attenuated the development of hypertension (systolic blood pressure, PTX: 145 ± 8 vs. vehicle (Veh): 235 ± 11 mmHg, after 38 days of treatment, P < 0.05, N = 5/group). This attenuation in hypertension was coupled with a decrease in the low-frequency spectra of systolic blood pressure variability (PTX: 1.23 ± 0.2 vs Veh: 3.05 ± 0.8 arbitrary units, P < 0.05, N = 5/group). Furthermore, systemic PTX administration decreased c-Fos expression within the hypothalamic paraventricular nucleus (PTX: 17 ± 4 vs. Veh: 70 ± 13 cells, P < 0.01, N = 5, PVN) and increased the total number of microglial branches (PTX: 2129 ± 242 vs. Veh: 1415 ± 227 branches, P < 0.05, N = 4/group). Acute central injection of PTX (20 μg) under urethane anesthesia caused a small transient decrease in blood pressure but did not change renal sympathetic nerve activity. Surprisingly, we found no detectable basal levels of plasma TNF-α in either PTX- or vehicle-treated animals. These results suggest that inflammation plays a role in renovascular hypertension and that PTX might act both peripherally and centrally to prevent hypertension.
Keywords: Hypertension; Inflammation; Pentoxifylline; Renovascular; Sympathetic nerve activity.