Protective effects of desipramine on alveolar bone in experimental periodontitis

Abstract

Background: Desipramine is a tricyclic antidepressant with immune-modulatory activity, whose effects on ligature-induced periodontitis are yet to be investigated. Hence, its actions on alveolar bone resorption, gingival collagen content and key inflammatory mediators were herewith analyzed.

Methods: A total of 60 male Wistar rats were randomly assigned into three groups: 1) control: rats without ligature treated with vehicle (saline); 2) ligature: rats with ligature-induced periodontitis treated with vehicle; 3) ligature + desipramine: rats with ligature-induced periodontitis treated with desipramine (20 mg/kg/d in vehicle). Mandibles and gingival tissues were collected 3 or 15 days after ligature insertion (or no ligature insertion for controls) and treatments. Alveolar bone resorption and gingival collagen fibers were histologically analyzed using either HE or picrosirius red staining. Gingival mRNA expressions of interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, matrix metalloproteinase (MMP)-9 and tissue inhibitor of metalloproteinase (TIMP)-1 were obtained through reverse transcription polymerase chain reaction. MMP-9 activity was analyzed by zymography.

Results: Alveolar bone loss was significantly reduced in the ligature + desipramine group (P < 0.05), whereas gingival collagen degradation was like the ligature group (P > 0.05). Desipramine administration downregulated mRNA expressions of IL-1β, iNOS, COX-2, and TIMP-1 when compared to vehicle alone in the ligature group (P < 0.05). MMP-9 expression and MMP-9/TIMP-1 ratio were similar among rats with ligature-induced periodontitis (P > 0.05); however, MMP-9 activity was lower in the group treated with desipramine (P < 0.05).

Conclusion: Desipramine administration reduced alveolar bone loss as histologically observed, and modulated key bone remodeling and inflammatory mediators in rats with ligature-induced periodontitis.

Keywords: bone resorption; collagen; desipramine; inflammation; periodontal diseases.

Figure 1.

Effect of a 15-day treatment with desipramine on alveolar bone loss in ligature-induced periodontitis in rats. A – Photomicrograph illustrating periodontal ligament in the furcation region of a non-ligated tooth in the control group. B – Photomicrograph illustrating bone loss in the furcation region of a ligated tooth in the ligature (vehicle) group. C – Photomicrograph illustrating bone loss in the furcation region of a ligated tooth in the ligature + desipramine group. Photomicrographs were stained with hematoxylin and eosin; original magnification x50. D - Desipramine decreased alveolar bone resorption in ligature-induced periodontitis; data are expressed as mean ± SD of periodontal ligament or bone loss area (mm²) around non-ligated and ligated teeth, respectively (n = 10 animals per group). *P<0.001 when compared to control and ligature + desipramine groups, according to ANOVA followed by Tukey’s test.

Figure 2.

Effect of a 15-day treatment with desipramine on gingival collagen content in ligature-induced periodontitis in rats. Histological sections represent collagen fibers in gingival connective tissue immediately above the bone crest in the mesial aspect of mandibular first molars (picrosirius red stain; original magnification x400): A – collagen fibers in connective tissue of a non-ligated tooth in the control group; B – collagen fibers in connective tissue of a ligated tooth in the ligature (vehicle) group; C – collagen fibers in connective tissue of a ligated tooth in the ligature+desipramine group. D – Desipramine did not protect collagen fibers integrity (percentage area) after ligature placement. Data are expressed as mean ± SD (n = 10 animals per group). *P<0.001 when compared to the control group, according to ANOVA followed by Tukey’s test.

Figure 3.

IL-1ß (A), iNOS (B) and COX-2 (C) mRNA levels (mRNA/GAPDH) in gingival tissues harvested from the control, ligature and ligature + desipramine groups. Samples were collected 3 days after the ligature placement, and the gene expression was detected using RT-PCR. Data are expressed as mean ± SD (n = 10 animals per group). *P<0.001 when compared to the control group; ^†P<0.05 when compared to both the control and ligature groups, according to ANOVA followed by Tukey’s test.

Figure 4.

Effects of desipramine on MMP-9 mRNA expression (A), TIMP-1 mRNA expression, MMP-9/TIMP-1 ratio (C) and MMP-9 activity (D) in gingival tissues harvested from the control, ligature and ligature + desipramine groups. Data are expressed as mean ± SD (n = 10 animals per group). *P<0.001 when compared to the control group; ^†P<0.01 when compared to both the control and ligature + desipramine groups, according to ANOVA followed by Tukey’s test.