Unilateral ligature-induced periodontitis causes endothelial dysfunction in rats

Paula Campi1, Simone Teixeira1, Maria Catelli de Carvalho1, Bruno Schneider Herrera2, Soraia Pereira Costa1, Luis Spolidorio2, Marcelo Muscara1. 1University of Sao Paulo, Sao Paulo, SP, Brazil, 2State Sao Paulo University, Araraquara, SP, Brazil

Introduction: Based on emerging evidence showing that periodontitis can affect cardio-circulatory parameters, we decided to evaluate the consequences of ligature-induced periodontitis on rat blood pressure (BP) and in vitro aorta reactivity.

Methods: The experimental protocols were approved by the local Ethics Committee for Animal Experimentation (CEUA-ICB; protocol number 154, book 2, page 24). Sixteen male Wistar rats (180-200 g) were anaesthetised with 80 mg/kg ketamine plus 16 mg/kg xylazine (i.p.). Unilateral periodontitis was induced in the animals by placing a subgingival cotton-ligature around the lower right first molar; sham operated animals (n=8) had the cotton ligature immediately removed after the procedure (Arch Oral Biol, 2011; 56: 41-7). Six days later, tail-cuff BP was measured, and on the 7th day, the animals were anaesthetised and subsequently euthanized by exsanguination. Thoracic aorta was dissected and cleaned from fat and connective tissue, and rings (4 mm length) were prepared and mounted in isolated tissue baths (containing Krebs solution at 37ºC and bubbled with O2/CO2) for measurement of isometric tension. Concentration-tension curves to cumulative additions of norepinephrine (NE) or acetylcholine (ACh) after NE pre-contraction were obtained. The participation of nitric oxide (NO) and cyclooxigenase-derived products was assessed by pre-incubating the vessel rings with either 100 μM L-NAME (non-selective NOS inhibitor), 1 μM 1400W (iNOS inhibitor), 10 μM indomethacin (non-selective COX inhibitor), 1 μM NS398 (COX-2 inhibitor) or 9 nM SC560 (COX-1 inhibitor).

Results: Periodontitis had no effect on BP, although resulted in significant decrease of the maximum responses (Emax) of the aorta rings to NE-induced contraction (2.16±0.13 vs. sham: 2.68±0.12 g; P<0.05) and ACh-induced dilatation (43.5±2.7 vs sham: 71.9±2.2%, P<0.001). These differences were not observed when endothelium was rubbed-off (in both groups, Ach-induced vasodilatation was abolished), or after pre-incubation of the vessels with either L-NAME, 1400W, indomethacin or NS398, but not SC560.

Conclusions: Although unilateral periodontitis in rats did not alter BP, endothelial dysfunction effectively occurred. This alteration was evident not only by the reduced aorta dilatation to ACh, but also by having affected the contractile response to NE. Based on the observed inhibitor effects, iNOS-derived NO and COX-2 products seem to be involved in the observed endothelial dysfunction.

Financial support: CNPq, FAPESP, CAPES.