Oxytocin alleviates periodontitis in adult rats.

OBJECTIVE: The objective of the study was to evaluate the expression of oxytocin receptors in normal and inflamed gingiva, as well as the effects of systemic administration of oxytocin in bone loss and gum inflammatory mediators in a rat model of experimental periodontitis. BACKGROUND DATA: Current evidence supports the hypothesis of a disbalance between the oral microbiota and the host's immune response in the pathogenesis of periodontitis. Increased complexity of the microbial biofilm present in the periodontal pocket leads to local production of nitrogen and oxygen-reactive species, cytokines, chemokines, and other proinflammatory mediators which contribute to periodontal tissue destruction and bone loss. Oxytocin has been suggested to participate in the modulation of immune and inflammatory processes. We have previously shown that oxytocin, nitric oxide, and endocannabinoid system interact providing a mechanism of regulation for systemic inflammation. Here, we aimed at investigating not only the presence and levels of expression of oxytocin receptors on healthy and inflamed gingiva, but also the effects of oxytocin treatment on alveolar bone loss, and systemic and gum expression of inflammatory mediators involved in periodontal tissue damage using ligature-induced periodontitis. Therefore, anti-inflammatory strategies oriented at modulating the host's immune response could be valuable adjuvants to the main treatment of periodontal disease. METHODS: We used an animal model of ligature-induced periodontitis involving the placement of a linen thread (Barbour flax 100% linen suture, No. 50; size 2/0) ligature around the neck of first lower molars of adult male rats. The ligature was left in place during the entire experiment (7 days) until euthanasia. Animals with periodontitis received daily treatment with oxytocin (OXT, 1000 µg/kg, sc.) or vehicle and/or atosiban (3 mg/kg, sc.), an antagonist of oxytocin receptors. The distance between the cement-enamel junction and the alveolar bone crest was measured in stained hemimandibles in the long axis of both buccal and lingual surfaces of both inferior first molars using a caliper. TNF-α levels in plasma were determined using specific rat enzyme-linked immunosorbent assays (ELISA). OXT receptors, IL-6, IL-1ß, and TNF-α expression were determined in gingival tissues by semiquantitative or real-time PCR. RESULTS: We show that oxytocin receptors are expressed in normal and inflamed gingival tissues in male rats. We also show that the systemic administration of oxytocin prevents the experimental periodontitis-induced increased gum expression of oxytocin receptors, TNF-α, IL-6, and IL-1ß (p < .05). Furthermore, we observed a reduction in bone loss in rats treated with oxytocin in our model. CONCLUSIONS: Our results demonstrate that oxytocin is a novel and potent modulator of the gingival inflammatory process together with bone loss preventing effects in an experimental model of ligature-induced periodontitis.

Deleterious effect of chronic high-dose ethanol intake on biomechanical bone properties and periodontal status.

To evaluate the effect of high-graduation chronic ethanol (EtOH) intake on bone and periodontal tissues of rats. Male Wistar rats (250 g) were divided into two groups of n = 12 each one. EtOH (5 ml of 3 g/kg) was administered to the experimental group by gastric gavage twice a day for 20 days and the control group received water under the same conditions. The rats were euthanized and used to perform biochemical determination in plasma and gingival tissue, and histological and biomechanical studies in the femur and mandibular tissues. Alcohol increased both TNFα (p < 0.01) and PGE2 (p < 0.05) in plasma and gingiva (p < 0.05) as compared to controls. In addition, EtOH increased the alveolar bone loss as evidenced by the increased distance between the cement enamel junction and the alveolar crest (p < 0.01), the lower % of interradicular bone expressed as bone area/total area (B.Ar/T.Ar, p < 0.05) and the larger periodontal space (p < 0.05), as compared to controls. Likewise, the mandibular microtomographic analysis in alcoholized rats revealed a lower % of interradicular bone volume/total volume (BV/TV, p < 0.05), greater trabecular separation (p < 0.05) and greater % trabecular porosity (p < 0.05) than controls. No biomechanical alteration was observed in lower jaws, while the femur of alcoholized rats presented a decrease in the structural bone properties (p < 0.001), as a systemic consequence of deterioration of the diaphyseal architecture (p < 0.01) without changes in material properties. The consumption of high doses of alcohol produces deleterious effects on periodontal tissues that could be due not only to local but also systemic effects.

Endocannabinoid System in the Neuroendocrine Response to Lipopolysaccharide-induced Immune Challenge.

The endocannabinoid system plays a key role in the intersection of the nervous, endocrine, and immune systems, regulating not only their functions but also how they interplay with each other. Endogenous ligands, named endocannabinoids, are produced "on demand" to finely regulate the synthesis and secretion of hormones and neurotransmitters, as well as to regulate the production of cytokines and other proinflammatory mediators. It is well known that immune challenges, such as exposure to lipopolysaccharide, the main component of the Gram-negative bacteria cell wall, disrupt not only the hypothalamic-pituitary-adrenal axis but also affects other endocrine systems such as the hypothalamic-pituitary-gonadal axis and the release of oxytocin from the neurohypophysis. Here we explore which actors and molecular mechanisms are involved in these processes.

Cannabis. Usos y aplicaciones en la práctica odontológica diaria: revisión de la literatura / Cannabis. Uses and applications in daily dental practice: a review of the literature

La evidencia científica presente en la literatura indica que el cannabis puede ser utilizado con fines terapéuticos para tratar distintas afecciones odontológicas. Dado el acceso sencillo a la cavidad bucal, las distintas formulaciones de cannabis pueden aplicarse de forma tópica. La aplicación local de dosis bajas de cannabis ha demostrado alta efectividad para tratar distintas afecciones bucales, constituyendo un tratamiento seguro con baja probabilidad de generar repercusiones sistémicas indeseadas. En la actualidad, está siendo incorporado a materiales convencionales de uso e higiene odontológica con la finalidad de aprovechar sus efectos terapéuticos. El cannabis tiene múltiples usos en odontología: como componen-te de enjuagues bucales y soluciones para la desinfección de conductos radiculares, en tratamientos de trastornos de ansiedad bucal, como complemento en terapias oncológicas, como analgésico para atenuar el dolor inflamatorio y el neuropático, como miorrelajante y condroprotector para tratar trastornos de articulación témporomandibular (ATM) y bruxismo, como osteomodulador para el tratamiento de patologías que comprometen la integridad ósea, como la enfermedad periodontal y la osteoporosis, y para la cicatrización ósea asociada a fracturas, extracciones dentarias e implantes, y como inmunomodulador con potencial terapéutico para tratar patologías autoinmunes como las enfermedades reumáticas. El trata-miento local con cannabis es efectivo, bien tolerado por el paciente y con pocos efectos adversos. Por lo tanto, se puede concluir que el cannabis aporta un enorme abanico de posibilidades terapéuticas para tratar distintas afecciones odontológicas, aunque aún se requiere mayor cantidad de estudios científicos que avalen su utilización en cada situación fisiopatológica particular (AU)

The scientific evidence present in the literature indicates that cannabis can be used for therapeutic purposes to treat different dental conditions. Given the easy access to the oral cavity, the different cannabis formulations can be applied topically. The local application of low doses of cannabis has shown high effectiveness in treating different oral conditions, constituting a safe treatment with a low probability of generating unwanted systemic repercussions. It is currently being incorporated into conventional materials for dental use and hygiene in order to take advantage of its therapeutic effects. Cannabis has multiple uses in dentistry: as a component of mouthwashes and solutions for disinfecting root canals, in the treatment of oral anxiety disorders, as a complement in oncological therapies, as an analgesic to reduce inflammatory and neuropathic pain, as a muscle relaxant and chondroprotective to treat temporomandibular joint disorders and bruxism, as an osteomodulator for the treatment of pathologies that compromise bone integrity, such as periodontal disease and osteoporosis, and or bone healing associated with fractures, dental extractions and implants, and as immunomodulator with therapeutic potential to treat autoimmune pathologies such as rheumatic diseases. Local treatment with cannabis is effective, well tolerated by the patient and with few adverse effects. Local treatment with cannabis is effective, well tolerated by the patient and with few adverse effects. Therefore, it can be concluded that cannabis provides an enormous range of therapeutic possibilities to treat different dental conditions, although more scientific studies are still required to support its use in each particular pathophysiological situation (AU)

Altered production of reproductive neuropeptides in rats subjected to chronic intermittent hypoxia.

Hypobaric hypoxia is a stressful condition known to decrease fertility both in humans and animals. However, the mechanism by which the hypothalamus-pituitary-gonad axis is altered remains unknown. The aim of the present study was to analyze the effects of chronic intermittent and continuous exposure to hypoxia on hypothalamic-pituitary-gonadal axis regulation in male rats. Thirty adult male Wistar rats were assigned to one of the following three groups: control group; chronic intermittent hypoxia: subjected to 600 mbar for 18 h/d five days a week; and chronic continuous hypoxia: subjected to 600 mbar for 23.5 hours/day seven days a week, for 30 days. Plasma luteinizing hormone and testosterone concentration, hypothalamic GnRh, Kiss1 and Rfrp3 mRNA levels and PGE2 content were determined. Levels of Rfrp3, a negative regulator of GnRH and LH release, were higher in intermittently exposed animals than in controls. Levels of Kiss1, a neuropeptide that stimulates the release of GnRH only increased in animals exposed to continuous hypoxia. Plasma luteinizing hormone and testosterone concentrations and body weight were lower in rats subjected to intermittent hypoxia as compared to the remaining groups. GnRh mRNA levels as well as PGE2 content remained unchanged in all groups. Taken together, results suggest that besides the well documented direct effects of hypoxia on the testes, infertility observed in male rats exposed to hypoxia may also be due to overexpression of negative regulators of GnRH and luteinizing hormone release. Intermittent, rather than continuous, to hypoxia exposure would seem to be more detrimental to fertility.

Mandibular biomechanical behavior of rats submitted to chronic intermittent or continuous hypoxia and periodontitis.

BACKGROUND: The aim of this study was to investigate the effects of exposure to continuous (CH) and intermittent (IH) hypoxia on biomechanical properties of the mandible and periodontal tissue of animals submitted to experimental periodontitis (EP) when applying loads in a hypoxic environment. METHODS: Adult female Wistar rats were exposed during 90 days to IH or CH (simulated high altitude of 4200 m above sea level). Fourteen days prior to the euthanasia, EP was induced to half of the animals of each group. RESULTS: Only in the rats with EP, IH decreased the maximum capacity of the mandible to withstand load and the limit of elastic load. Indicators of intrinsic properties of the bone material were significantly reduced by both types of hypoxia in rats with EP. Hypoxia enhanced the alveolar bone loss induced by EP in the buccal side of the mandible, without showing additional effects in lingual or interradicular bone. Hypoxia increased prostaglandin E2 content in gingival tissue of healthy animals and further elevated the E2 levels increased by EP. CONCLUSIONS: When periodontitis is present, hypoxic stress induces a decrease in mineral properties that ultimately affects the ability of the mandible to resist load, mainly during intermittent exposure to hypoxia. These effects on bone may be related to the higher levels of prostaglandin E2 reached in the surrounding gingival tissue. The findings of this study may stimulate strategies to prevent unwanted effects of hypoxia on periodontal tissues.

Presence of Trichomonas spp. in oral ulcerations of a patient with kidney transplant. A case report.

Mucosal ulcerations are an oral complication that can often affect kidney transplant patients, mostly due to the effect of immunosuppression. It has been frequently reported drug-induced ulceration or lymphoproliferative disorders with buccal manifestations however, some unusual disorders should also be considered, such as fungal infections, viruses, as well as opportunistic infection by other microorganisms. Determining the etiology and differential diagnose from other causes of mouth ulcers is very important for the adequate treatment of said lesion. Dental health of patients should also be taken into the account prior to the transplant surgery, since periodontal pockets are the main niche of microbial reservoir. Moreover, mixed with oral microbiota, parasites such as Trichomonas spp. can be found in the dental plaque of patients with periodontal disease. Particularly, Trichomonas spp. are anaerobic motile-flagellated protozoa that can both induce tissue damage and exacerbate preexistent injuries in vaginal and oral mucosa. Parasitic infection in the oral cavity has not been well studied and it is thought to be underreported. In the present study we report the first case in literature of presence of Trichomonas spp. as a potential etiological factor of the oral ulcerations of a kidney transplanted patient that remitted after antibiotic treatment. Key words:Immunosuppression, protozoan, buccal lesion, oral mucosa, kidney transplant.

Signs of alveolar bone damage in early stages of periodontitis and its prevention by stimulation of cannabinoid receptor 2. Model in rats.

The aims of the present study were, first, to identify signs of alveolar bone damage in early stages of experimental periodontitis (EP) and, second, to assess its possible prevention by treatment with cannabinoid receptor 2 agonist HU 308. Experimental periodontitis was induced by injections of lipopolysaccharide (LPS) (1mg/ml) in gums surrounding maxillary and mandibular first molar, 3 days per week, and untreated controls were kept for comparison. Then, a 3-week study was conducted including eighteen new rats (six rats per group): 1) controls; 2) experimental periodontitis rats; and 3) experimental periodontitis rats treated daily with HU 308 (500 ng/ml). After euthanasia, alveolar bone loss was assessed by morphometric and histomorphometric techniques, and the content of prostaglandin E2 (PGE2) in gingival tissue was evaluated by radioimmunoassay. The first signs of alveolar bone loss were apparent at 3 weeks of experimental periodontitis (ρ<0.05) in the mandibular first molar, but there was no detectable change at 1 week, leading us to establish 3 weeks as an early stage of experimental periodontitis. Rats subjected to 3-week experimental periodontitis showed less interradicular bone volume, less whole bone perimeter and fewer bone formation areas, and higher periodontal space height, bone resorption areas, number of osteoclasts and gingival content of prostaglandin E2 than controls, while HU 308 prevented, at least partially, the deleterious effects (ρ<0.001). We can conclude that a 3-week term of lipopolysaccharide-induced periodontitis in rats provides a valid model of the early stage of the disease, as emerging damage is observed in bone tissue. Furthermore, harmful effects at 3 weeks could be prevented by local stimulation of cannabinoid receptor 2, before greater damage is produced.

El objetivo del presente trabajo fue, en primer lugar, identificar signos de daño óseo alveolar en estadios tempranos de periodontitis experimental y, en segundo lugar, evaluar su posible prevención mediante el tratamiento con el agonista del receptor cannabinoide 2, HU 308. La periodontitis experimental fue inducida por inyecciones de lipopolisacárido (1mg/ml) en la encía circundante al primer molar maxilar y mandibular, 3 días por semana, en tanto que controles no tratados fueron mantenidos para la comparación. Posteriormente, un estudio de 3 semanas con dieciocho nuevas ratas (seis por grupo) fue desarrollado: 1) controles; 2) ratas con periodontitis experimental, y 3) ratas con periodontitis experimental tratadas diariamente con HU 308 (500ng/ml). Luego de la euthanasia, la pérdida ósea alveolar fue evaluada por técnicas morfométricas e histomorfométricas, y el contenido de prostaglandina E2 en el tejido gingival fue determinado por radioinmunoensayo. Los primeros signos de pérdida ósea alveolar fueron evidentes a las 3 semanas de inducción de periodontitis experimental (ρ<0.05) en el primer molar mandibular, mientras que no hubo cambios detectables luego de 1 semana de inducción, hecho que nos condujo a establecer a las 3 semanas como un estadio temprano de periodontitis experimental, Las ratas sometidas a perdiodontitis experimental de 3 semanas mostraron menor volumen óseo interradicular, menor perímetro óseo y menos áreas de formación ósea, y mayor altura del espacio periodontal, más áreas de reabsorción ósea, mayor número de osteoclastos y mayor contenido gingival de prostaglandina E2, en comparación a los controles, mientras que el tratamiento con HU 308 previno, al menos parcialmente, los efectos deletéreos (ρ<0.001). Podemos concluir que el término de 3 semanas de periodontitis inducida por lipopolisacárido es un modelo válido de estadio inicial de la enfermedad experimental, dado que se evidencia daño emergente en el tejido óseo. Asimismo, los efectos deletéreos de 3 semanas podrían ser prevenidos por la estimulación local del receptor cannabinoide 2, antes que un daño mayor sea producido.

Signs of alveolar bone damage in early stages of periodontitis and its prevention by stimulation of cannabinoid receptor 2. Model in rats / Signos de daño óseo alveolar en estadios tempranos de periodontitis y su prevención por estimulación del receptor cannabinoide 2. Modelo en ratas microcisalhamento do cimento resinoso

ABSTRACT The aims of the present study were, first, to identify signs of alveolar bone damage in early stages of experimental periodontitis (EP) and, second, to assess its possible prevention by treatment with cannabinoid receptor 2 agonist HU 308. Experimental periodontitis was induced by injections of lipopolysaccharide (LPS) (1mg/ml) in gums surrounding maxillary and mandibular first molar, 3 days per week, and untreated controls were kept for comparison. Then, a 3-week study was conducted including eighteen new rats (six rats per group): 1) controls; 2) experimental periodontitis rats; and 3) experimental periodontitis rats treated daily with HU 308 (500 ng/ml). After euthanasia, alveolar bone loss was assessed by morphometric and histomorphometric techniques, and the content of prostaglandin E2 (PGE2) in gingival tissue was evaluated by radioimmunoassay. The first signs of alveolar bone loss were apparent at 3 weeks of experimental periodontitis (ρ<0.05) in the mandibular first molar, but there was no detectable change at 1 week, leading us to establish 3 weeks as an early stage of experimental periodontitis. Rats subjected to 3-week experimental periodontitis showed less interradicular bone volume, less whole bone perimeter and fewer bone formation areas, and higher periodontal space height, bone resorption areas, number of osteoclasts and gingival content of prostaglandin E2 than controls, while HU 308 prevented, at least partially, the deleterious effects (ρ<0.001). We can conclude that a 3-week term of lipopolysaccharide-induced periodontitis in rats provides a valid model of the early stage of the disease, as emerging damage is observed in bone tissue. Furthermore, harmful effects at 3 weeks could be prevented by local stimulation of cannabinoid receptor 2, before greater damage is produced.

RESUMEN El objetivo del presente trabajo fue, en primer lugar, identificar signos de daño óseo alveolar en estadios tempranos de periodontitis experimental y, en segundo lugar, evaluar su posible prevención mediante el tratamiento con el agonista del receptor cannabinoide 2, HU 308. La periodontitis experimental fue inducida por inyecciones de lipopolisacárido (1mg/ml) en la encía circundante al primer molar maxilar y mandibular, 3 días por semana, en tanto que controles no tratados fueron mantenidos para la comparación. Posteriormente, un estudio de 3 semanas con dieciocho nuevas ratas (seis por grupo) fue desarrollado: 1) controles; 2) ratas con periodontitis experimental, y 3) ratas con periodontitis experimental tratadas diariamente con HU 308 (500ng/ml). Luego de la euthanasia, la pérdida ósea alveolar fue evaluada por técnicas morfométricas e histomorfométricas, y el contenido de prostaglandina E2 en el tejido gingival fue determinado por radioinmunoensayo. Los primeros signos de pérdida ósea alveolar fueron evidentes a las 3 semanas de inducción de periodontitis experimental (ρ<0.05) en el primer molar mandibular, mientras que no hubo cambios detectables luego de 1 semana de inducción, hecho que nos condujo a establecer a las 3 semanas como un estadio temprano de periodontitis experimental, Las ratas sometidas a perdiodontitis experimental de 3 semanas mostraron menor volumen óseo interradicular, menor perímetro óseo y menos áreas de formación ósea, y mayor altura del espacio periodontal, más áreas de reabsorción ósea, mayor número de osteoclastos y mayor contenido gingival de prostaglandina E2, en comparación a los controles, mientras que el tratamiento con HU 308 previno, al menos parcialmente, los efectos deletéreos (ρ<0.001). Podemos concluir que el término de 3 semanas de periodontitis inducida por lipopolisacárido es un modelo válido de estadio inicial de la enfermedad experimental, dado que se evidencia daño emergente en el tejido óseo. Asimismo, los efectos deletéreos de 3 semanas podrían ser prevenidos por la estimulación local del receptor cannabinoide 2, antes que un daño mayor sea producido.

Participation of TRPV1 in the activity of the GnRH system in male rats.

GnRH neuron activity is under the influence of multiple stimuli, including those coming from the endocannabinoid and the immune systems. Since it has been previously suggested that some of the main elements controlling the GnRH pulse generator possess the TRPV1 receptor, the aim of the present study was to evaluate the participation of the hypothalamic TRPV1, through its pharmacological blockade, in the activity of the hypothalamic-pituitary-testicular axis in male rats under basal or acute inflammatory conditions. Our hypothesis was based on the idea that the hypothalamic TRPV1 participates in the synthesis of the main neuromodulatory signals controlling GnRH, and therefore the reproductive axis. Our results showed that the hypothalamic TRPV1 blockade induced pro-inflammatory effects by increasing Tnfα and Il-1ß mRNA hypothalamic levels and inhibited the reproductive axis by affecting Gnrh, Kiss1 and Rfrp3 mRNA levels and decreasing plasma levels of luteinizing hormone and testosterone under basal conditions, without significant additive effects in rats exposed to systemic LPS. Altogether, these results suggest that the hypothalamic TRPV1 receptor participates in the regulation of the GnRH system, probably by modulating immune-dependent mechanisms.

A new target to ameliorate the damage of periodontal disease: The role of transient receptor potential vanilloid type-1 in contrast to that of specific cannabinoid receptors in rats.

BACKGROUND: Transient receptor potential vanilloid type-1 (TRPV1) is expressed in oral tissues cells and its activity can be regulated by inflammation products and anandamide. The aim of the present study was to evaluate the effects of blocking TRPV1 or specific cannabinoid receptors 1 (CB1r) and 2 (CB2r) on periodontal status of rats subjected to experimental periodontitis (EP). METHODS: Male rats were distributed in groups 1) control, 2) lipopolysaccharide-induced EP (LPS), and 3) LPS plus capsazepine (Capz, TRPV1 antagonist) application (LPS+Capz). EP was induced by injections of LPS (1 mg/mL) around first molars and treatment was performed with Capz (2 µg/mL) applied locally during 6 weeks. Additional experiment was performed by applying CB1r and CB2r antagonists (AM251 and AM630) to rats with EP. RESULTS: Capz prevented alveolar bone loss (ABL) on the external crests and in the interradicular bone of the first molars (periodontal space height: LPS, 270.7 ± 33.5µm versus LPS+Capz, 216.4 ± 19.9 µm; P <0.01). Inflammatory mediators, like tumor necrosis factor-alpha and prostaglandin E2 , increased by LPS-induced EP, were diminished in gingival tissue of rats treated with Capz. In contrast, application of AM251 and AM630 exacerbated ABL and gingival inflammatory mediators, increased by LPS, altering also biomechanical properties. CONCLUSIONS: TRPV1 blockade attenuates periodontal impairment in EP rats, since it reduces local inflammation, unlike CB1r and CB2r blockade. This work lays the foundation for developing therapeutics in humans based on the pharmacological manipulation of these receptors to treat periodontal disease.

Changes in PGE2 signaling after submandibulectomy alter post-tooth extraction socket healing.

Saliva is very important to oral health, and a salivary deficit has been shown to bring serious problems to oral health. There is scant information about the mechanisms through which salivary glands participate in post-tooth extraction socket healing. Therefore, the aim of the present study was to investigate the effect of submandibulectomy (SMx), consisting of the ablation of submandibular and sublingual glands (SMG and SLG, respectively), on PGE2 signaling and other bone regulatory molecules, such as OPG and RANKL, involved in tooth extraction socket healing. Male Wistar rats, 70 g body weight, were assigned to an experimental (subjected to SMx) or a control group (sham operated). One week later, the animals in both groups underwent bilateral extraction of the first mandibular molars. The effect of SMx on different stages of socket healing after tooth extraction (7, 14, and 30 days) was studied by evaluating some parameters of inflammation, including PGE2 and its receptors, and of bone metabolism, as well as by performing bone biomechanical studies. SMx increased TNFα and PGE2 content as well as cyclooxygenase-II (COX-II) expression in tooth socket tissue at almost all the studied time points. SMx also had an effect on mRNA expression of PGE2 receptors at the different time points, but did not significantly alter osteoprotegerin (OPG) and RANKL mRNA expression at any of the studied time points. In addition, an increase in bone mass density was observed in SMx rats compared with matched controls, and the structural and mechanical bone properties of the mandibular socket bone were also affected by SMx. Our results suggest that the SMG/SLG complex regulates cellular activation and differentiation by modulating the production of molecules intervening in tooth extraction socket repair, including the PGE2 signaling system, which would therefore account for the higher density and resistance of the newly formed bone in SMx rat.

Pharmacological augmentation of endocannabinoid signaling reduces the neuroendocrine response to stress.

Activation of the hypothalamic-pituitary-adrenal axis (HPA) is critical for survival when the organism is exposed to a stressful stimulus. The endocannabinoid system (ECS) is currently considered an important neuromodulator involved in numerous pathophysiological processes and whose primary function is to maintain homeostasis. In the tissues constituting the HPA axis, all the components of the ECS are present and the activation of this system acts in parallel with changes in the activity of numerous neurotransmitters, including nitric oxide (NO). NO is widely distributed in the brain and adrenal glands and recent studies have shown that free radicals, and in particular NO, may play a crucial role in the regulation of stress response. Our objective was to determine the participation of the endocannabinoid and NOergic systems as probable mediators of the neuroendocrine HPA axis response to a psychophysical acute stress model in the adult male rat. Animals were pre-treated with cannabinoid receptors agonists and antagonists at central and systemic level prior to acute restraint exposure. We also performed in vitro studies incubating adrenal glands in the presence of ACTH and pharmacological compounds that modifies ECS components. Our results showed that the increase in corticosterone observed after acute restraint stress is blocked by anandamide administered at both central and peripheral level. At hypothalamic level both cannabinoid receptors (CB1 and CB2) are involved, while in the adrenal gland, anandamide has a very potent effect in suppressing ACTH-induced corticosterone release that is mainly mediated by vanilloid TRPV1 receptors. We also observed that stress significantly increased hypothalamic mRNA levels of CB1 as well as adrenal mRNA levels of TRPV1 receptor. In addition, anandamide reduced the activity of the nitric oxide synthase enzyme during stress, indicating that the anti-stress action of endocannabinoids may involve a reduction in NO production at hypothalamic and adrenal levels. In conclusion, an endogenous cannabinoid tone maintains the HPA axis in a stable basal state, which is lost with a noxious stimulus. In this case, the ECS dampens the response to stress allowing the recovery of homeostasis. Moreover, our work further contributes to in vitro evidence for a participation of the endocannabinoid system by inhibiting corticosterone release directly at the adrenal gland level.

The Process of Acclimation to Chronic Hypoxia Leads to Submandibular Gland and Periodontal Alterations: An Insight on the Role of Inflammatory Mediators.

The exposition to hypoxia is a stressful stimulus, and the organism develops acclimation mechanisms to ensure homeostasis, but if this fails, it leads to the development of pathological processes. Considering the large number of people under hypoxic conditions, it is of utmost importance to study the mechanisms implicated in hypoxic acclimation in oral tissues and the possible alteration of some important inflammatory markers that regulate salivary and periodontal function. It is the aim of the present study to analyze submandibular (SMG) and periodontal status of animals chronically exposed to continuous (CCH) or intermittent (CIH) hypoxia in order to elucidate the underlying molecular mechanisms that may lead to hypoxic acclimation. Adult Wistar rats were exposed to CCH or CIH simulating 4200 meters of altitude during 90 days. Salivary secretion was decreased in animals exposed to hypoxia, being lower in CIH, together with increased prostaglandin E2 (PGE2) content, TBARS concentration, and the presence of apoptotic nuclei and irregular secretion granules in SMG. AQP-5 mRNA levels decreased in both hypoxic groups. Only the CCH group showed higher HIF-1α staining, while CIH alone exhibited interradicular bone loss and increased concentration of the bone resorption marker CTX-I. In summary, animals exposed to CIH show a worse salivary secretion rate, which related with higher levels of PGE2, suggesting a negative role of this inflammatory mediator during hypoxia acclimation. We link the weak immunorreactivity of HIF-1α in CIH with improper hypoxia acclimation, which is necessary to sustaining SMG physiology under this environmental condition. The alveolar bone loss observed in CIH rats could be due mainly to a direct effect of PGE2, as suggested by its higher content in gingival tissue, but also to the indirect effect of hyposalivation. This study may eventually contribute to finding therapeutics to treat the decreased salivary flow, improving in that way oral health.

Deleterious effect of chronic continuous hypoxia on oral health.

OBJECTIVE: To evaluate the effect of chronic continuous hypoxia (CCH) in alveolar bone and its correlation with the inflammatory markers which play a key role in the development of periodontitis. MATERIAL AND METHODS: Wistar rats were exposed to CCH (600mbar, 3 months). Macroscopic and histological analyses of alveolar bone were performed, together with measurement of oxidative stress and inflammatory parameters in gums and submandibular glands (SMG). RESULTS: HCC induced cortical alveolar bone loss, decreased interradicular bone volume and increased the periodontal ligament height compared to control rats (p<0.05). CCH enhanced iNOS activity in gums (from 2735,04±662,96 nmol/min/mg proteins to 4289,58±915,63 p<0.05) and in SMG (from 56,71±12,05 nmol/min/mg proteins to 90,15±21,78 p<0.05). PGE2 did not change in gums or in SMG by means of CCH, while TNFα decreased in gums (p<0.05). Regarding oxidative stress, thiobarbituric acid reactive species concentration in CCH animals was higher both in gums as in SMG, and catalase activity was decreased in SMG. CONCLUSION: Higher iNOS activity both in gums and SMG under CCH could be associated with the alveolar bone loss observed. The increase in oxidative stress occurring in SMG and gums, together with a lower antioxidant capacity might indicate a deleterious effect of HX in oral health.

Anti-Inflammatory and Osteoprotective Effects of Cannabinoid-2 Receptor Agonist HU-308 in a Rat Model of Lipopolysaccharide-Induced Periodontitis.

BACKGROUND: Anti-inflammatory and immunologic properties of cannabinoids have been reported in several tissues. Expression of cannabinoid receptor Type 2 was reported in osteoblasts and osteoclasts, suggesting a key role in bone metabolism. The aim of this study is to assess the effect of treatment with cannabinoid-2 receptor agonist HU-308 in the oral health of rats subjected to lipopolysaccharide (LPS)-induced periodontitis. METHODS: Twenty-four rats were distributed in four groups (six rats per group): 1) control rats; 2) sham rats; 3) rats submitted to experimental periodontitis (LPS); and 4) rats submitted to experimental periodontitis and treated with HU-308 (LPS+HU). In groups LPS and LPS+HU, periodontitis was induced by LPS (1 mg/mL) injected into the gingival tissue (GT) of maxillary and mandibular first molars and into the interdental space between the first and second molars, 3 days per week for 6 weeks. In group LPS+HU, HU-308 (500 ng/mL) was applied topically to the GT daily. RESULTS: Alveolar bone loss resulting from LPS-induced periodontitis was significantly attenuated with HU-308 treatment (LPS+HU), measured by macroscopic and histologic examination. Treatment also reduced gingival production of inflammatory mediators augmented in LPS-injected rats, such as: 1) inducible nitric oxide (iNOS) activity (LPS: 90.18 ± 36.51 pmol/minute/mg protein versus LPS+HU: 16.37 ± 4.73 pmol/minute/mg protein; P <0.05); 2) tumor necrosis factor alpha (LPS: 185.70 ± 25.63 pg/mg protein versus LPS+HU: 95.89 ± 17.47 pg/mg protein; P <0.05); and 3) prostaglandin E2 (PGE2) (LPS: 159.20 ± 38.70 pg/mg wet weight versus LPS+HU: 71.25 ± 17.75 pg/mg wet weight; P <0.05). Additionally, HU-308 treatment prevented the inhibitory effect of LPS-induced periodontitis on the salivary secretory response to pilocarpine. Moreover, iNOS activity and PGE2 content, which were increased by LPS-induced periodontitis in the submandibular gland, returned to control values after HU-308 treatment. CONCLUSION: This study demonstrates anti-inflammatory, osteoprotective, and prohomeostatic effects of HU-308 in oral tissues of rats with LPS-induced periodontitis.

Effects of saliva on early post-tooth extraction tissue repair in rats.

The aim of the present study was to perform a biochemical, histological, and histomorphometrical evaluation of the mechanisms involved in tissue repair in rats subjected to submandibulectomy-induced hyposialia, 24, 48, and 72 hours of post-tooth extraction. We studied the correlation between the lack of submandibular saliva and the modulation of inflammatory mediators involved in tissue repair, such as prostaglandin E2 , nitric oxide (NO), and tumor necrosis factor alpha (TNF-α). Rats with hyposialia showed a delay in socket healing, slow replacement of the clot with granulation tissue, and fewer cells and collagen fibers, concomitant with a longer inflammatory process, as compared to controls. The lack of saliva induced by submandibulectomy modified the levels of prostaglandin E2 , NO, and TNF-α, and tissue response in the early stages of wound healing compared to controls, and could thus determine alterations in later osteogenic response. Our results allow concluding that hyposialia modulates the parameters of inflammation studied here, and that it is essential for optimal healing. Therefore, these findings provide evidence for the importance of submandibular saliva to final bone socket healing.

Lead intoxication under environmental hypoxia impairs oral health.

We have reported that chronic lead intoxication under hypoxic environment induces alveolar bone loss that can lead to periodontal damage with the subsequent loss of teeth. The aim of the present study was to assess the modification of oral inflammatory parameters involved in the pathogenesis of periodontitis in the same experimental model. In gingival tissue, hypoxia increased inducible nitric oxid synthase (iNOS) activity (p < .01) and meanwhile lead decreased prostaglandin E2 (PGE2) content (p < .05). In submandibular gland (SMG), iNOS activity was enhanced by lead and PGE2 content was increased by both lead and hypoxia (p < .01) and even more by combined treatments (p < .001). In the SMG, hypoxia stimulated angiogenesis (p < .01) with blood extravasation. Adrenal glands were 22% bigger in those animals exposed to lead under hypoxic conditions. Results suggest a wide participation of inflammatory markers that mediate alveolar bone loss induced by these environmental conditions. The lack of information regarding oral health in lead-contaminated populations that coexist with hypoxia induced us to evaluate the alteration of inflammatory parameters in rat oral tissues to elucidate the link between periodontal damage and these environmental conditions.

Chronic alcohol consumption alters periodontal health in rats.

BACKGROUND: The aim of this study was to assess the effects of chronic alcohol consumption on periodontitis development in rats. METHODS: Periodontal disease was experimentally induced by lipopolysaccharide (LPS; 2 mg/ml) injections into the gingival tissue around first upper and lower molar's neck, and into the interdental space between first and second molars. This protocol was repeated for 6 weeks on days 1, 3, and 5 of each week. Chronic alcohol consumption was induced by 20% ethanol (EtOH) as the only liquid source during 4 months. RESULTS: Chronic alcohol consumption by itself increased alveolar bone loss and biological mediators of periodontal disease such as prostaglandin E2 (PGE2 ) content on gingival tissue, and inducible nitric oxide synthase activity plus PGE2 content in submandibular gland. Unexpectedly, alcohol consumption did not increase the damage evoked by the proved model of LPS injections for periodontitis induction. CONCLUSIONS: Results suggest 20% alcohol consumption during 4 months generates differential effects on oral health of rats, depending on its pathophysiological state: It would exacerbate the inflammatory condition when periodontal damage is absent, but it would not when damage is installed.