© Birkhäuser Verlag, Basel, 2008 Inflamm. res. 57, Supplement 1 (2008) S29–S30 1023-3830/08/01S29-02 DOI 10.1007/s00011-007-0615-1

Inflammation Research

Cetirizine, a histamine H1 receptor antagonist, decreases the first stage of orthodontic tooth movement in rats I. Križnar1, Š. Sprogar2, M. Drevenšek3, T. Vaupotic4 and G. Drevenšek2 1

Department of Dental Diseases and Endodontology Institute of Pharmacology and Experimental Toxicology 3 Department of Orthodontics 4 Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Korytkova 2, 1000 Ljubljana, Slovenia, Fax: ++386 15437331, e-mail: [email protected] 2

Published Online First 14 March 2008

Introduction Force application during orthodontic tooth movement induces inflammatory changes in dental and paradental tissues, particularly in the periodontal ligament (PDL) and the alveolar bone [1]. Orthodontic forces decrease blood flow due to the compression of the vascular system. As a result ischemia, interruption of nutrition and cell death occur leading to the formation of a necrotic zone – hyalinized zone [2]. Inflammation, as a local response to tissue injury follows, comprising of vascular and cellular changes [1]. These changes lead to the removal of the necrotic tissue and remodelling of the PDL and the alveolar bone, which is mediated through the release of inflammatory mediators [2, 3]. One of the mediators is probably histamine. The aim of the study was to determine the role of cetirizine, a selective H1 receptor antagonist in orthodontic tooth movement in rats. Materials and methods

The histamine H1 gene expression levels were assessed by means of relative RT-PCR using subtype-specific primers. Relative gene expression levels of the histamine H1 mRNA were normalized against the GAPDH mRNA as a control. For statistical analysis, two way ANOVA and Bonferroni’s post-test and Student t-test were used. This investigation was approved by the Veterinary Administration of the Republic of Slovenia (No. 323-02-234/2005/2) and complied with local animal legislation.

Results and discussion Group I treated with cetirizine showed significantly less (p < 0.05) tooth movement on day 7 when compared to Group II. Groups I and II showed significantly higher amount of tooth movement compared to Group III on days 7, 14, 21, 28, 35 and 42 (p < 0.001). The distance between the teeth significantly increased (p < 0.001) in Group III from day 0 to day 42 (Fig. 1), due to the natural distal drift of the molars. Gene expression level of histamine H1 receptors mRNA was significantly higher on days 14 and 42 compared to day 0

Male Wistar rats (300–340 g) were divided into three groups. Under general anaesthesia [4], a superelastic closed coil spring was applied between the teeth in animals of Groups I (n = 7) and II (n = 20). Group I was treated daily with cetirizine (10 mg/kg p.o.) while Group II had saline (1 ml/kg i.p.) daily. In Group III (n = 7) no appliance was used and the rats were treated daily with saline (1 ml/kg i.p.). A superelastic closed coil spring (25 cN, wire diameter 0.15 mm, GAC International, New York, USA) was placed between the first maxillary molar and the incisors [5]. It was fixed to the upper left first molar with a stainless steel ligature wire (diameter 0.25 mm, Dentaurum, Ispringen, Germany) and to the incisors by surgical steel wire (4-0, multifilament, W310, Ethicon, Johnson&Johnson, New Jersey, USA). The distance between the teeth was measured on days 0, 7, 14, 21, 28, 35 and 42 using a digitronic calliper (precision 0.01 mm, Wilson & Wolpert, Utrecht, The Netherlands). In Group II five animals were killed on days 0, 14, 28 and 42. Tissue samples of the alveolar bone with all three molars and their PDL were taken. For isolation of total RNA from tissue samples, TRIzol reagent (Invitrogen) was used according to the manufacturer’s specifications [6].

Correspondence to: I. Križnar

Fig. 1. Tooth movement in Groups I, II and III ± SEM; * p < 0.05.

S30

Inflamm. res. Supplement 1 (2008)

(p < 0.001), but was not significantly different on day 28 compared to day 0 (Fig. 2). Orthodontic tooth movement comprises of several stages [2, 7]. Cetirizine, a selective histamine H1 antagonist, reduced tooth movement on day 7, which coincides with the phase of acute inflammation of paradental tissues during tooth movement, while in the later stages it does not have a significant role. The gene expression level of histamine H1 receptors varied during the experiment. It was significantly higher on days 14 and 42 compared to day 0. However it seems histamine plays an important role through its action via histamine H1 receptors only in initial stage of orthodontic tooth movement, probably through its pro-inflammatory action. Since antihistamines are widely distributed medications in use, it is important to know their influences on orthodontic treatment [8]. References [1] Vandevska-Radunovic V. Neural modulation of inflammatory reactions in dental tissues incident to orthodontic tooth movement. Eur J Orthod; 21: 231–47. [2] Krishnan V, Davidovitch Z. Cellular, molecular, and tissue-level reactions to orthodontic force. Am J Orthod Dentofacial Orthop 2006; 129(4): 469.e1-32. [3] Meikle MC. The tissue, cellular, and molecular regulation of orthodontic tooth movement: 100 years after Carl Sandstedt. Eur J Orthod 2006; 28: 221–40. [4] Drevenšek M, Sprogar S, Boras I, Drevenšek G. Effects of endothelin antagonist tezosentan on orthodontic tooth movement in rats. Am J Orthod and Dentofacial Orthop 2006; 129: 555–8. [5] Sprogar Š, Volk J, Drevenšek M, Drevenšek G. The effects of TBC3214, a selective endothelin ETA receptor antagonist, on orthodontic tooth movement in rats. Eur J Orthod 2007; 29: 605–8.

Fig. 2. Gene expression level of histamine H1 receptors (HRH1) on days 0, 14, 28 and 42 (*p < 0.001).

[6] Kim JE, Nakashima K, de Crombrugghe B. Transgenic Mice Expressing a Ligand-Inducible Cre Recombinase in Osteoblasts and Odontoblasts: A New Tool to Examine Physiology and Disease of Postnatal Bone and Tooth. Am J Pathol. 2004; 165(6): 1875–82. [7] Ren Y, Maltha JC, Kuijpers-Jagtman AM. The rat as a model for orthodontic tooth movement-a critical review and a proposed solution. Eur J Orthod 2004; 26: 483–90. [8] Blaiss MS. Antihistamines: treatment selection criteria for pediatric seasonal allergic rhinitis. Allergy Asthma Proc 2005; 26: 95–102.

To access this journal online: http://www.birkhauser.ch/IR