Kinin generation in the gingival inflammatory response to topically applied bacterial lipopolysaccharides

Non-canonical signalling and roles of the vasoactive peptides angiotensins and kinins

GPCRs (G-protein-coupled receptors) are among the most important targets for drug discovery due to their ubiquitous expression and participation in cellular events under both healthy and disease conditions. These receptors can be activated by a plethora of ligands, such as ions, odorants, small ligands and peptides, including angiotensins and kinins, which are vasoactive peptides that are classically involved in the pathophysiology of cardiovascular events. These peptides and their corresponding GPCRs have been reported to play roles in other systems and under pathophysiological conditions, such as cancer, central nervous system disorders, metabolic dysfunction and bone resorption. More recently, new mechanisms have been described for the functional regulation of GPCRs, including the transactivation of other signal transduction receptors and the activation of G-protein-independent pathways. The existence of such alternative mechanisms for signal transduction and the discovery of agonists that can preferentially trigger one signalling pathway over other pathways (called biased agonists) have opened new perspectives for the discovery and development of drugs with a higher specificity of action and, therefore, fewer side effects. The present review summarizes the current knowledge on the non-canonical signalling and roles of angiotensins and kinins.

Sleep-related movement disorders

Several movement disorders may occur during nocturnal rest disrupting sleep. A part of these complaints is characterized by relatively simple, non-purposeful and usually stereotyped movements. The last version of the International Classification of Sleep Disorders includes these clinical conditions (i.e. restless legs syndrome, periodic limb movement disorder, sleep-related leg cramps, sleep-related bruxism and sleep-related rhythmic movement disorder) under the category entitled sleep-related movement disorders. Moreover, apparently physiological movements (e.g. alternating leg muscle activation and excessive hypnic fragmentary myoclonus) can show a high frequency and severity impairing sleep quality. Clinical and, in specific cases, neurophysiological assessments are required to detect the presence of nocturnal movement complaints. Patients reporting poor sleep due to these abnormal movements should undergo non-pharmacological or pharmacological treatments.

Bradykinin potentiates cytokine-induced prostaglandin biosynthesis in osteoblasts by enhanced expression of cyclooxygenase 2, resulting in increased RANKL expression

OBJECTIVE

Bradykinin (BK) stimulates bone resorption in vitro and synergistically potentiates interleukin-1 (IL-1)-induced bone resorption and prostaglandin (PG) formation, suggesting that kinins are important in inflammation-induced bone loss. The present study was undertaken to study 1) the role of the kinin B1 and B2 receptors in the synergistic interaction with IL-1 and tumor necrosis factor alpha (TNFalpha), 2) the molecular mechanisms involved in synergistic enhancement of PG formation, and 3) the effects of kinins on cytokine-induced expression of RANKL, RANK, and osteoprotegerin (OPG) (the latter being crucial molecules in osteoclast differentiation).

METHODS

Formation of PGs, expression of enzymes involved in arachidonic acid metabolism, and expression of RANKL, RANK, and OPG were assessed in the human osteoblastic cell line MG-63 and in mouse calvarial bones. The role of NF-kappaB and MAP kinases was studied using pharmacologic inhibitors.

RESULTS

PGE(2) formation and cyclooxygenase 2 (COX-2) protein expression were induced by IL-1beta and potentiated by kinins with affinity for the B1 or B2 receptors, resulting in PGE(2)-dependent enhancement of RANKL. The enhancements of PGE(2) formation and COX-2 were markedly decreased by inhibition of p38 and JNK MAP kinases, whereas inhibition of NF-kappaB resulted in abolishment of the PGE(2) response with only slight inhibition of COX-2.

CONCLUSION

Kinin B1 and B2 receptors synergistically potentiate IL-1- and TNFalpha-induced PG biosynthesis in osteoblasts by a mechanism involving increased levels of COX-2, resulting in increased RANKL. The synergistic stimulation is dependent on NF-kappaB and MAP kinases. These mechanisms might help to explain the enhanced bone resorption associated with inflammatory disorders, including that in rheumatoid arthritis.

The effect of catecholamine precursor L-dopa on sleep bruxism: a controlled clinical trial

The putative role of the dopaminergic system in sleep bruxism (SB) was studied in a double-blind clinical trial by using low doses of short-term L-dopa in combination with benserazide. We recorded 10 patients with SB in our sleep laboratory for 3 consecutive nights. The first night was for habituation to the laboratory environment. During the second and the third nights, the patients received two doses of either L-dopa or a placebo in a crossover fashion: the first dose 1 h before bedtime and the second, 4 h after the first one. The order of administration was reversed in half the patients. The efficacy of L-dopa was analyzed by using multilevel models. L-Dopa resulted in a significant decrease in the average number of bruxism episodes per hour of sleep, as well as in a significant reduction in the average value of the root-mean-square (RMS) electromyography (EMG) level per bruxism burst. This indicates that L-dopa exerts an attenuating effect on SB. In addition, L-dopa caused a reduction in the variance in RMS values, which suggests that L-dopa normalizes the EMG activity patterns associated with SB.

Effects and interactions of tumour necrosis factor alpha and bradykinin on interleukin-1 production in gingival fibroblasts

Effects of and interactions between tumour necrosis factor alpha (TNF alpha) and bradykinin (BK) on production of interleukin-1 (IL-1 alpha, IL-1 beta) in human gingival fibroblasts were studied. The cytokine TNF alpha induced production of cell-associated IL-1 alpha and IL-1 beta in gingival fibroblasts, with IL-1 beta being most abundant. Addition of BK, in the presence of TNF alpha, for 1 h and 6 h, respectively, synergistically enhanced the TNF alpha induced IL-1 beta production, whereas BK alone did not induce IL-1 production. Similar to BK, two phorbol esters, phorbol 12,13 dibutyrate (PDBu) and phorbol 12-myristate-13-acetate (PMA) which are known to stimulate protein kinase C (PKC), synergistically enhanced the TNF alpha induced IL-1 beta production in the gingival fibroblasts. On the contrary, a phorbol ester which does not activate protein kinase C, 13-phorbolacetate (13-PA), did not potentiate the TNF alpha induced IL-1 beta production. Similar to BK, the phorbol esters (PMA, PDBu, 13-PA) alone did not induce IL-1 beta production in the gingival fibroblasts. The results indicate that TNF alpha induces production of cell-associated IL-1 in gingival fibroblasts, which can be upregulated by a PKC dependent pathway.

Effect of Campylobacter rectus LPS on plasminogen activator-plasmin system in human gingival fibroblast cells

The plasminogen activator (PA)-plasmin system is implicated in the degradation of the extracellular matrix in inflammation through activation of metalloproteases and prekallikrein. We examined the activation of the PA-plasmin system in human gingival fibroblast cells (Gin-1 cells) following treatment with lipopolysaccharide (LPS) from Campylobacter rectus, which is frequently detected at sites of periodontal disease. The C. rectus LPS stimulated the plasmin activity in the conditioned medium of Gin-1 cells in a time- and dose-dependent manner, and C. rectus LPS also stimulated the PA activity in the conditioned medium. The PA produced by Gin-1 cells was determined to be urokinase PA (uPA), as preincubation of Gin-1 conditioned medium with anti-uPA antiserum completely inhibited the PA activity while that with anti-tPA antiserum had no inhibitory effect. The concentration of PA inhibitor-1 (PAI-1) in the conditioned medium was decreased by the addition of C. rectus LPS. Therefore, the enhancement of plasmin activity in the conditioned medium was dependent on increased uPA activity via the decrease of the PAI-1 level of Gin-1 cells treated with C. rectus LPS. Furthermore, the conditioned medium of Gin-1 cells treated with C. rectus LPS showed significantly increased kallikrein activity, indicating the conversion of prekallikrein to kallikrein, which converts kininogen into kinin. These findings suggest that C. rectus LPS is a potent stimulator of inflammation of gingival tissue which acts through stimulation of the PA-plasmin system.

Regulation of bone metabolism by the kallikrein-kinin system, the coagulation cascade, and the acute-phase reactants

Inflammation-induced localized bone resorption in diseases such as marginal and apical periodontitis, rheumatoid arthritis, and osteomyelitis is due to activation and recruitment of osteoclasts by locally produced cytokines and inflammatory mediators. Thus several interleukins (1, 3, 4, 6, and 11), tumor necrosis factors (alpha, beta), colony-stimulating factors (M and GM), leukemia inhibitory factor, gamma-interferon, and transforming growth factor-beta have effects on bone resorption and bone formation in vivo and in vitro. The kallikrein-kinin system and the coagulation cascade are also activated in inflammation. We have found that peptides produced in the kallikrein-kinin system (bradykinin, kallidin) and thrombin, the end product in the coagulation cascade, can stimulate bone resorption in vitro. The stimulatory effect of bradykinin is linked both to B1 and B2 bradykinin receptors. Both kinins and thrombin stimulate prostaglandin biosynthesis in bone parallel with the bone resorptive effect. The stimulatory effect of bradykinin on bone resorption is completely lost when the prostaglandin response is abolished, whereas thrombin can stimulate bone resorption both via prostaglandin-dependent and independent mechanisms. In addition, bradykinin and thrombin act in concert with interleukin-1 to synergistically stimulate bone resorption and prostaglandin biosynthesis. We also have found that one of the acute-phase reactants, haptoglobin, can stimulate bone resorption in vitro, indicating the possibility of generalized bone loss in chronic inflammatory diseases. Moreover, haptoglobin synergistically potentiates bradykinin-induced and thrombin-induced prostanoid biosynthesis in osteoblasts. These observations indicate that the rate of bone resorption in inflammation-induced bone loss may not be due to a single factor but to the concerted action of several local or systemic factors.

Bradykinin-2 receptor-mediated release of 3H-arachidonic acid and formation of prostaglandin E2 in human gingival fibroblasts

Bradykinin stimulated production of prostaglandin E2 (PGE2) and the release of 3H-arachidonic acid by gingival fibroblasts in a time- and dose-dependent manner. The effect on PGE2 biosynthesis was seen already after 15 seconds and was maximal after 5 minutes. Several structurally unrelated inhibitors of arachidonic acid metabolism via the cyclooxygenase pathway totally abolished the PGE2 response to bradykinin. The stimulation of PGE2 formation was seen at and above 10 nmol/l of bradykinin. Des-Arg9-bradykinin was 100-fold less potent compared to bradykinin. Des-Arg9-Leu8-bradykinin did not antagonize bradykinin-induced PGE2 formation. Met-Lys-bradykinin and Lys-bradykinin also enhanced PGE2 formation in gingival fibroblasts. The stimulatory action of bradykinin on 3H-arachidonic acid release was observed after 30 s and progressively increased for at least 15 min. The stimulatory effect on 3H-arachidonic acid release by bradykinin was seen at and above 10 nmol/l, whereas des-Arg9-bradykinin was without effect up to a concentration of 1 mumol/l. Indomethacin did not affect bradykinin-induced 3H-arachidonic acid release. These data show that bradykinin, via a B2-receptor-mediated pathway, can stimulate arachidonic acid release and subsequent prostanoid formation in gingival fibroblasts. Consequently, gingival fibroblasts may contribute, by a bradykinin-regulated reaction, to the enhanced amounts of prostanoids found in gingival tissues and crevicular fluids in patients with periodontal diseases.

Mucositis prevention by selective elimination of oral flora in irradiated head and neck cancer patients

Mucositis induced by irradiation is the reactive inflammatory-like process of the oropharyngeal mucous membranes following irradiation. Bacteria colonizing the oral tissues are thought to contribute to this inflammatory process. The eradication of Gram-negative bacilli (selective elimination of oral flora) in fifteen comparably irradiated head and neck cancer patients was found to be associated with a significant reduction in mucositis compared with two groups of 15 patients receiving either placebo or chlorhexidine rinsing. Criteria used were the extent of local mucositis signs (mucositis score), as well as generalized side-effects such as the need of nasogastric tube feedings following severe feeding problems. Mucositis signs were confined to erythema only in all selectively decontaminated patients. No pseudomembranes were observed and artificial feeding was completely prevented. These promising results need further confirmation in larger (multicenter) studies.

Characterization and immunobiologic activities of lipopolysaccharides from periodontal bacteria

Bacterial surface structures play a critical role in the initiation of infectious diseases. Various surface components of pathogenic bacteria have been reported to be involved in host injury. There is a great deal of evidence incriminating certain Gram-negative, anaerobic bacteria present in the gingival crevice as etiologic agents of human periodontal diseases. We have isolated endotoxic cellular components from suspected periodontopathic bacteria and examined their immunobiological activities. Lipopolysaccharides (LPS) and lipid-associated proteoglycans (LPG) were prepared from whole cells by the phenol-water and butanol-water procedures, respectively. LPS from Bacteroides gingivalis, B. intermedius, B. oralis, and B. loescheii, Fusobacterium nucleatum and F. necrophorum, and Actinobacillus (Haemophilus) actinomycetemcomitans were found to possess biological activities comparable with those of LPS from E. coli K235 in terms of activation of Limulus lysate, B-cell mitogenicity, polyclonal B-cell activation, induction of bone resorption, and IL-1 production by macrophages. These LPS contained mainly sugars, amino sugars, and fatty acids. No heptose or 2-keto-3-deoxyoctonate (KDO) was detected in the Bacteroides LPS, while LPS from Actinobacillus and Fusobacterium species contained significant amounts of heptose as well as small quantities of KDO. Bacteroides LPS were clearly mitogenic for spleen cells of C3H/HeJ mice, which are non-responsive to LPS from E. coli, A. actinomycetemcomitans, and Fusobacterium species. Furthermore, polymyxin B was found to abrogate the mitogenic activity of LPS from E. coli, Actinobacillus, and Fusobacterium species, but not those from Bacteroides species. Spleen cells from both C3H/HeN and C3H/HeJ mice responded to all butanol-water-extracted LPG preparations, including those from E. coli, A. actinomycetemcomitans, and Fusobacterium species. It may be concluded that LPS and LPG isolated from suspected periodontopathic bacteria possess marked immunobiological potencies on lymphoreticular and bone cells.