Anti-inflammatory effect of the endocannabinoid anandamide in experimental periodontitis and stress in the rat.

OBJECTIVE: Periodontitis is an infectious disease leading to inflammation and destruction of tissue surrounding and supporting the tooth. The progress of the inflammatory response depends on the host's immune system and risk factors such as stress. The aim of the present study was to investigate the role of the endocannabinoid anandamide (AEA) in experimental periodontitis with restraint stress, since the endocannabinoid system is known to modulate the hypothalamo-pituitary-adrenal axis as well as immune functions and has been found in human gingival tissues. METHODS: Experimental periodontitis was induced by ligature around first inferior molars and immobilization stress for 2 h twice daily for 7 days in a rat model. RESULTS: Corticosterone plasma levels, locomotor activity, adrenal gland weight and bone loss were increased in periodontitis and stress groups, and there was also less weight gain. The inflammatory parameters such as prostaglandin E(2) (radioimmunoassay), nitric oxide (radioconversion of (14)C-arginine), tumor necrosis factor (TNF)-α (ELISA) and interleukin (IL)-1ß (Western blot) measured in the gingival tissue were significantly increased in the periodontitis groups compared to the control group. Local injection of AEA (10(-8)M, 30 µl) decreased corticosterone plasma levels and the content of the cytokines TNF-α and IL-1ß in gingival tissue in periodontitis-stress groups. These AEA-induced inhibitions were mediated by CB(1) and CB(2) cannabinoid receptors since the injection of both antagonists together, AM251 (10(-6)M) and AM630 (10(-6)M) in 30 µl, prevented these effects. CONCLUSION: The endocannabinoid AEA diminishes the inflammatory response in periodontitis even during a stressful situation.

Role of the endocannabinoid system in ethanol-induced inhibition of salivary secretion.

AIM: The aim of the present study was to determine whether the endocannabinoid system could be involved in the ethanol-induced inhibition of salivation in adult male Wistar rats. METHODS: Salivary secretion induced by different concentrations of methacholine, a cholinergic agonist, and the endocannabinoid arachidonoyl ethanolamide (anandamide, AEA) production in the submandibular gland (SMG) were determined in rats after ethanol (3 g/kg) administration by gastric gavage. To study the participation of cannabinod receptors in ethanol action, we evaluated methacholine-induced salivary secretion after ethanol administration when CB1 or CB2 receptors were blocked by intra-SMG injections of their selective antagonists AM251 and AM630, respectively. Additionally, we evaluated the in vitro effect of ethanol (0.1 M) on SMG production of cAMP, alone or combined with AM251 or AM630. RESULTS: Acute ethanol administration increased AEA production in SMG and also inhibited the methacholine-induced saliva secretion that was partially restored by intraglandular injection of AM251 or AM630. In addition, ethanol significantly reduced the forskolin-induced increase in cAMP content in SMG in vitro while treatment with AM251 blocked this response. CONCLUSION: We conclude that the inhibitory effect produced by ethanol on submandibular gland salivary secretion is mediated, at least in part, by the endocannabinoid system.

Inhibition of salivary secretion by activation of cannabinoid receptors.

It is known that marijuana use decreases saliva secretion. Therefore, we hypothesized that cannabinoid receptors (CBs) are located in salivary glands to mediate that effect. In these experiments, we used the submandibular gland (SMG) of male rats, which is one of the major salivary glands. Mammalian tissues contain at least two types of CBs, CB1 and CB2, mainly located in the nervous system and peripheral tissues, respectively. Both receptors are coupled to Gi protein and respond by inhibiting the activity of adenylyl cyclase. We demonstrated that both CB1 and CB2 are present in the SMG, each showing specific localizations. The best-known endocannabinoid is anandamide (AEA), which binds with high affinity to CB1 and CB2. We showed that AEA markedly reduced forskolin-induced increase of cAMP content in vitro. This effect was blocked by AM251 and AM630 (CB1 and CB2 antagonists, respectively), indicating that both receptors are implicated in SMG physiology. In addition, we showed that AEA injected intraglandularly to anesthetized rats inhibited norepinephrine (NE)- and methacholine (MC)-stimulated saliva secretion in vivo and that both AM251 or AM630 prevented the inhibitory action of AEA. Also, the intraglandular injection of AM251 increased saliva secretion induced by lower doses of NE or MC. This increase was synergized after coinjection with AM630. Therefore, we concluded that AEA decreases saliva secretion in the SMG acting through CB1 and CB2 receptors.

Host neuro- immuno-endocrine responses in periodontal disease.

Periodontitis is a chronic inflammatory complex disease caused by microorganisms. It may be influenced by diverse systemic disorders, environmental, genetic and socio-psychological factors with the ability to alter the balance of the host neuro-immunoendocrine responses. It is characterized by the progressive destruction of the tooth supporting apparatus leading to tooth loss, with possible impact on general health. Starting with a brief description of the periodontium, etiopathogenesis, repair processes and several physiological mechanisms and their disarray on periodontium response to bacterial challenge. Following, the negative effects of stress on the disease and some remarks on the recently discovered effects of oxytocin that modulate stress response and its role in individual coping mechanisms to stress. We also focus on the participation of components and functions of endocannabinoid system with anti-inflammatory actions on gingiva. Finally, a discussion that may link between diabetes, cardiovascular diseases, stroke and metabolic syndrome associated with periodontal disease; all of them sharing a common denominator that is inflammation and oxidative stress.

Participation of the endocannabinoid system in lipopolysaccharide-induced inhibition of salivary secretion.

OBJECTIVE: The aim of the present paper was to assess whether lipopolysaccharide (LPS)-induced inhibition of salivary secretion involves the activation of the endocannabinoid system and the participation of tumor necrosis factor (TNF)alpha in the submandibular gland. DESIGN: Pharmacological approaches were performed by using CB1 and/or CB2 cannabinoid receptor antagonists, AM251 and AM630, respectively, injected into the submandibular gland, to study the participation of the endocannabinoid system in LPS inhibitory effects on metacholine-induced salivary secretion. To assess the participation of TNFalpha on LPS inhibitory effects, salivary secretion was studied in LPS treated rats after the intraglandular injection of etanercept, a soluble form of TNF receptor which blocks TNFalpha action. Finally, to evaluate the possible interplay between endocannabinoids and TNFalpha on the submandibular gland function reduced during LPS challenge, the salivary secretion was studied after the intraglandular injection of this cytokine alone or concomitantly with AM251 and AM630. RESULTS: AM251 and AM630, injected separately or concomitantly, partially prevented LPS-induced inhibition of salivation. Also, anandamide synthase activity was increased in submandibular glands extracted from rats 3h after LPS injection, suggesting that the endocannabinoid system was activated in response to this challenge. On the other hand, etanercept, prevented the inhibitory effect of LPS on salivary secretion and moreover, TNFalpha injected intraglandularly inhibited salivary secretion, being this effect prevented by AM251 and AM630 injected concomitantly. CONCLUSION: The present results demonstrate the participation of the endocannabinoid system and TNFalpha on salivary responses during systemic inflammation induced by LPS.

Decrease in salivary secretion by radiation mediated by nitric oxide and prostaglandins.

OBJECTIVE: In the present work, we evaluated the effect of exposing the submandibular glands (SMG) to radiation, studying different functional parameters such as salivary secretion, nitric oxide (NO) production, reactive oxygen species formation, prostaglandin (PGE) content and apoptosis. METHODS: We irradiated rats in the head and neck region with a single dose of gamma-ray radiation of 15 Gy. Two hours after radiation, we measured norepinephrine-induced salivary secretion. After that, the SMG were dissected, and in this tissue, we measured the activity of NO synthase (NOS), the PGE content, the amount of reactive oxygen species, apoptotic cells and mitochondrial inducible NOS (iNOS) expression. RESULTS: We found that radiation decreased salivary secretion when 10 and 30 microg/kg of norepinephrine was administered via the right femoral vein. We observed that iNOS activity was reduced and PGE content increased after radiation in SMG, indicating that NO and PGEs may participate in salivary secretion. The expression of mitochondrial NOS was increased after radiation leading to the formation of large amounts of NO that acts as a proapoptotic signal. In fact, we observed an augmentation in apoptotic cells. In this study, we also observed an increase in lipid peroxidation induced by radiation that may contribute to tissue damage. CONCLUSIONS: Our results indicate that radiation induced a decrease in salivary secretion and SMG iNOS activity, meanwhile the PGE content, the lipid peroxidation and apoptosis increased in the tissue. These modifications decrease salivary secretion.