Role of the activation of the nuclear enzyme poly(ADP-ribose) polymerase in the pathogenesis of periodontitis

Role of poly(ADP-ribose) polymerase activation in the pathogenesis of periodontitis in diabetes

AIM

The aetiology of progressive periodontitis in diabetes has not yet been elucidated. We previously demonstrated that nitrosative stress is increased in diabetic rats with periodontitis. Nitrosative stress induces poly(ADP-ribose) polymerase (PARP) activation. Here, we demonstrated the involvement of PARP activation in diabetic periodontitis and detailed the therapeutic effects of PARP inhibitor.

MATERIALS AND METHODS

Experimental periodontitis was induced by placing a nylon thread ligature. Half of the normal and diabetic rats received the PARP inhibitor, 1,5-isoquinolinediol, for 2 weeks. Gingival PARP activation was detected by immunostaining for poly(ADP-ribose). Periodontitis was evaluated by gingival inflammatory cell infiltration, inflammatory gene expressions and micro-CT analyses.

RESULTS

Although both periodontitis and the presence of diabetes increased PARP activation in the gingiva, diabetic rats with periodontitis had the highest activation of PARP. Diabetic rats with periodontitis also showed significant increases in monocyte/macrophage invasion into the gingiva, inflammatory gene expressions, nitrotyrosine-positive cells in the gingiva and alveolar bone loss, all of which were suppressed by treatment with the PARP inhibitor.

CONCLUSIONS

These results indicate the involvement of PARP activation in the pathogenesis and aggravation of periodontal disease in diabetes and suggest the therapeutic potential of PARP inhibition for treating periodontal disease, especially in patients with diabetes.

Future prospects of systemic host modulatory agents in periodontal therapy

Periodontitis is an inflammatory disease caused by microbial infection that leads to destruction of supporting tissues of the teeth. The periodontal tissue destruction is a result of both microbial activity as well as host response. The best chance for clinical improvement may come from implementing complementary treatment strategies that target different aspects of the periodontal balance. Host response modulation, in combination with conventional treatment, offers to restore the balance between health and disease progression in the direction of a healing response. Various host modulatory therapies (HMT) have been developed or proposed to block pathways responsible for periodontal tissue break down. The newer drugs like bortezomib, infliximb, etanercept, vasoactive intestinal peptide, nitric oxide synthase inhibitors and denosumab are developed as a result of better understanding of pathogenesis of inflammatory tissue destruction and may represent the future of periodontal therapy. This review article focuses on the potential systemic host modulatory agents that target cell signalling pathways, cytokines and enzymes.

Efficacy of subantimicrobial-dose doxycycline against nitrosative stress in chronic periodontitis

AIM

To evaluate the effectiveness of subantimicrobial-dose doxycycline (SDD) as an adjunct to scaling and root planing (SRP) treatment against the nitrosative stress of moderate to advanced chronic periodontitis.

METHODS

Adults with untreated chronic periodontitis (n=174) were randomly administered SRP+SDD (n=87) (20 mg of doxycycline twice daily) or SRP+placebo (n=87) treatment for 3 months. At baseline and after 3 months, the probing depths (PD), bleeding on probing (BOP) and clinical attachment level (CAL) were measured, and a gingivomucosal biopsy was collected to assay the induction of nitric oxide synthase (iNOS) and 3-nitrotyrosine (3NT), and blood was collected to assay for total nitrites and nitrates (NO(x)) and 3NT.

RESULTS

Compared to baseline, at the completion of treatment, significant decreases in the levels of tissue iNOS and 3NT and serum NO(x) and 3NT were observed in both groups. SRP+SDD yielded a greater reduction in the gingivomucosal and serum nitrosative stress markers than did SRP+placebo. PD, BOP, and CAL reduction were correlated with the nitrosative stress parameters.

CONCLUSION

On a short-term basis, SDD therapy may be used as an adjunct to SRP treatment against nitrosative stress in moderate to advanced chronic periodontitis.

Involvement of nitrosative stress in experimental periodontitis in diabetic rats

AIM

Periodontal disease is highly prevalent and severe in diabetic patients, and is considered one of the diabetic complications. To elucidate how periodontitis progresses in diabetes, we examined an animal model of periodontitis in diabetic rats.

MATERIALS AND METHODS

Two weeks after the induction of diabetes by streptozotocin, surgical nylon thread was ligated around the cervical portion of the unilateral maxillary second molar to induce periodontitis. Periodontitis was evaluated 2 weeks after the ligation by gingival blood flow, mRNA expressions, Western blot analysis, histological examination and micro CT.

RESULTS

Ligation-induced severe periodontitis in the diabetic rats, which was apparently shown by the increase of TNF-α and iNOS mRNA expressions and inflammatory cell infiltration in the gingiva and alveolar bone loss. The number of nitrotyrosine, a footprint of nitrosative stress, -positive cells was significantly higher in the periodontitis of the diabetic rats compared with that in the normal rats. Western blot analysis confirmed that the nitrotyrosine was increased in the periodontitis of the diabetic rats.

CONCLUSIONS

This is the first study to confirm increased nitrosative stress due to periodontitis in diabetic rats. Nitrosative stress may play a crucial role in the exacerbation of periodontitis in diabetic patients.

Effects of verbascoside, biotechnologically purified by Syringa vulgaris plant cell cultures, in a rodent model of periodontitis

Objectives

Verbascoside has previously been characterized as an effective scavenger of active free radicals and an inhibitor of lipid peroxidation. In the present study, we have investigated the effects of verbascoside from Syringa vulgaris in a rat model of ligature-induced periodontitis.

Methods

Male Sprague–Dawley rats were lightly anaesthetized with pentobarbitone (35 mg/kg). Sterile, 2-0 black braided silk thread was placed around the cervix of the lower left first molar and knotted medially. Animals received vebascoside 2 mg/kg orally, daily for 8 days.

Key findings

On the eighth day after placement of the ligature, we evaluated several markers of inflammation: (i) myeloperoxidase activity, (ii) thiobarbituric acid-reactant substance measurements, (iii) NF-κB expression, (iv) iNOS expression, (v) the nitration of tyrosine residues, (vi) activation of the nuclear enzyme poly(ADP-ribose) polymerase, (vii) Bax and Bcl-2 expression and (viii) a degree of gingivomucosal tissue injury. Oral administration of verbascoside (2 mg/kg daily for 8 days) significantly decreased all of the parameters of inflammation as described above.

Conclusions

These results demonstrate that verbascoside exerts an anti-inflammatory role during experimental periodontitis and is able to ameliorate the tissue damage associated with ligature-induced periodontitis.

Effects of Hypericum Perforatum, in a rodent model of periodontitis

BACKGROUND

Hypericum perforatum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. In this study we evaluate the effect of Hypericum perforatum in animal model of periodontitis.

METHODS

Periodontitis was induced in adult male Sprague-Dawley rats by placing a nylon thread ligature around the lower 1st molars. Hypericum perforatum was administered at the dose of 2 mg/kg os, daily for eight days. At day 8, the gingivomucosal tissue encircling the mandibular first molar was removed.

RESULTS

Periodontitis in rats resulted in an inflammatory process characterized by edema, neutrophil infiltration and cytokine production that was followed by the recruitment of other inflammatory cells, production of a range of inflammatory mediators such as NF-κB and iNOS expression, the nitration of tyrosine residues and activation of the nuclear enzyme poly (ADP-ribose) polymerase; apoptosis and the degree of gingivomucosal tissues injury. We report here that Hypericum perforatum exerts potent anti-inflammatory effects significantly reducing all of the parameters of inflammation as described above.

CONCLUSIONS

Taken together, our results clearly demonstrate that treatment with Hypericum reduces the development of inflammation and tissue injury, events associated with periodontitis.

Local osteoprotegerin gene transfer to periodontal tissue inhibits lipopolysaccharide-induced alveolar bone resorption

BACKGROUND AND OBJECTIVE

Osteoclastogenesis is primarily activated by receptor activator of nuclear factor kappaB ligand (RANKL) and is inhibited by osteoprotegerin (OPG). A previous study demonstrated that local OPG gene transfer to periodontal tissue inhibited RANKL-mediated osteoclastogenesis and experimental tooth movement. In the present study, we tested the hypothesis that local OPG gene transfer to the periodontium can neutralize RANKL activity induced by lipopolysaccharide injection, thereby inhibiting osteoclastogenesis and diminishing alveolar bone resorption in experimental periodontal disease.

MATERIAL AND METHODS

Seven-week-old male Wistar rats received an injection of lipopolysaccharide or phosphate-buffered saline in the palatal gingiva of the upper first molars on both the right and left sides. An inactivated haemagglutinating virus of Japan (HVJ) envelope vector containing a mouse OPG expression plasmid [pcDNA3.1(+)-mOPG] or mock vector was injected periodically into the palatal periodontal tissue of the upper first molars.

RESULTS

Lipopolysaccharide injection induced severe periodontal bone resorption. Local OPG gene transfer induced OPG production, and osteoclastogenesis was inhibited. Local OPG gene transfer significantly decreased alveolar bone resorption.

CONCLUSION

Osteoprotegerin gene transfer to periodontal tissue inhibited osteoclastogenesis and alveolar bone resorption in lipopolysaccharide-induced experimental periodontal disease.

Poly (ADP-ribose) polymerase activation and circulatory shock

Sepsis is associated with increased production of reactive oxidant species. Oxidative and nitrosative stress can lead to activation of the nuclear enzyme poly (ADP-ribose) polymerase (PARP), with subsequent loss of cellular functions. Activation of PARP may dramatically lower the intracellular concentration of its substrate, NAD thus slowing the rate of glycolysis, electron transport and subsequently ATP formation. This process can result in cell dysfunction and cell death. In addition, PARP enhances the expression of various pro-inflammatory mediators, via activation of NF-kappaB, MAP kinase and AP-1 and other signal transduction pathways. Preclinical studies in various rodent and large animal models demonstrate that PARP inhibition or PAR deficiency exerts beneficial effects on the haemodynamic and metabolic alterations associated with septic and haemorrhagic shock. Recent human data also support the role of PARP in septic shock: In a retrospective study in 25 septic patients, an increase in plasma troponin level was related to increased mortality risk. In patients who died, significant myocardial damage was detected, and histological analysis of heart showed inflammatory infiltration, increased collagen deposition, and derangement of mitochondrial criptae. Immunohistochemical staining for poly(ADP-ribose) (PAR), the product of activated PARP was demonstrated in septic hearts. There was a positive correlation between PAR staining and troponin I; and a correlation of PAR staining and LVSSW. Thus, there is significant PARP activation in animal models subjected to circulatory shock, as well as in the hearts of septic patients. Based on the interventional studies in animals and the correlations observed in patients we propose that PARP activation may be, in part responsible for the cardiac depression and haemodynamic failure seen in humans with severe sepsis. Interestingly, recent studies reveal that the protective effects of PARP inhibitors are predominant in male animals, and are not apparent in female animals. Oestrogen, by providing a baseline inhibitory effect on PARP activation, may be partially responsible for this gender difference.

5-aminoisoquinolin-1(2H)-one, a water-soluble poly (ADP-ribose) polymerase (PARP) inhibitor reduces the evolution of experimental periodontitis in rats

BACKGROUND

Poly (ADP-ribose) polymerase (PARP), a nuclear enzyme activated by strand breaks in DNA, plays an important role in the tissue injury associated with ischaemia-reperfusion and inflammation. Recent studies have demonstrated that PARP activation plays a crucial role in the pathogenesis of acute periodontal injury.

AIM

We have investigated the effect of 5-aminoisoquinolin-1(2H)-one (5-AIQ), a water-soluble PARP inhibitor, in a rat model of periodontitis.

MATERIALS AND METHODS

Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day eight, the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis.

RESULTS AND CONCLUSIONS

Ligation significantly induced an increased neutrophil infiltration and a positive staining for PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of 5-aminoisoquinolin-1(2H)-one (5-AIQ) (5 mg/kg daily for eight days) significantly decreased all of the parameters of inflammation as described above. This suggests that inhibition of PARP may represent a novel approach for the treatment of periodontal disease.

Chronic hyperglycemia predisposes to exaggerated inflammatory response and leukocyte dysfunction in Akita mice

The role of polymorphonuclear neutrophils (PMN) in mediating diabetic tissue damage to the periodontium was investigated in a novel model of chronic hyperglycemia, the Akita mouse. Induction of acute peritoneal inflammation in wild-type (WT) and Akita mice resulted in exaggerated IL-6 response in Akita mice (2.9-fold increase over WT values) and a markedly increased chemokine response (KC, 2.6-fold; MCP-1, 2.6-fold; and MIP-1alpha, 4.4-fold increase over WT values). Chemotaxis to both fMLP and WKYMVm was significantly reduced in isolated Akita PMN compared with WT PMN as measured in a Boyden chamber. Superoxide release in contrast was significantly increased in Akita PMN as measured with cytochrome c reduction. Bone marrow-derived Akita PMN showed partial translocation of p47phox to the cell membrane without external stimulation, suggesting premature assembly of the superoxide-producing NADPH oxidase in hyperglycemia. In vivo studies revealed that ligature-induced periodontal bone loss is significantly greater in Akita mice compared with WT. Moreover, intravital microscopy of gingival vessels showed that leukocyte rolling and attachment to the vascular endothelium is enhanced in periodontal vessels of Akita mice. These results indicate that chronic hyperglycemia predisposes to exaggerated inflammatory response and primes leukocytes for marginalization and superoxide production but not for transmigration. Thus, leukocyte defects in hyperglycemia may contribute to periodontal tissue damage by impairing the innate immune response to periodontal pathogens as well as by increasing free radical load in the gingival microvasculature.

Pyrrolidine dithiocarbamate reduced experimental periodontitis

Nuclear factor-kappaB (NF-kappaB) is a transcription factor which plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to injury and inflammation. Dithiocarbamates are antioxidants which are potent inhibitors of NF-kappaB. We postulated that pyrrolidine dithiocarbamate (PDTC) would attenuate inflammation. In the present study, we have investigated the effects of PDTC, in a rat model of periodontitis. Periodontitis was induced in rats by placing around the lower left first molar a 2/0 braided silk. At day eight the gingivomucosal tissue encircling the mandibular first molar was removed for biochemical and histological analysis. At day eight ligations significantly induced an increase neutrophil infiltration as well as the gingivomucosal tissue expression of TNF-alpha and iNOS as well as nitrotyrosine formation and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone destruction. Intraperitonial injection of PDTC (10 mg/kg daily for eight days) significantly reduced all of the parameters of inflammation as described above. These data demonstrate that PDTC exerts an anti-inflammatory role during experimental periodontitis and is able to ameliorate the tissue damage associated with ligature-induced periodontitis.

Cloricromene, a coumarine derivative, reduced the development of periodontitis in rats

Recent studies have demonstrated that cloricromene, a coumarin derivative, exerts protective effects in models of inflammation and shock. Tumour necrosis factor plays a pivotal role in the induction of genes involved in physiological processes, as well as in the response to inflammation. We investigated the effect of cloricromene in a rat model of periodontitis. Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day 8 the gingivomucosal tissue encircling the mandibular first molar was removed for evaluation of tumour necrosis factor production, neutrophil infiltration, tissue permeability, nitrotyrosine formation, poly (ADP-ribose) polymerase activation, radiography and histology. Ligation significantly induced an increased tumour necrosis factor production, neutrophil infiltration and a positive staining for nitrotyrosine formation and poly (ADP-ribose) polymerase activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone erosion as evaluated by radiography analysis. Intraperitonal injection of cloricromene (10 mg/kg daily for 8 days) significantly decreased all of the parameters of inflammation as described above. This suggests that cloricromene treatment, which reduced tumour necrosis factor production, may be of benefit in the treatment of periodontitis.

Host response modulation in the management of periodontal diseases

OBJECTIVE

To review the biological mechanisms and clinical utility of therapeutic modulation of the host response in the management of periodontal diseases.

MATERIAL AND METHODS

A search of MEDLINE-PubMed was performed up to and including December 2004. The search was limited to in vitro, experimental animal and clinical studies published in English. The selection criteria included all levels of available evidence: systematic reviews, randomised-controlled clinical trials, controlled clinical trials, prospective and retrospective cohort studies and case reports of human and experimental animal studies.

RESULTS

Six targets for non-microbial chemotherapeutic intervention were identified. Clinical trials have demonstrated the ability of non-steroidal anti-inflammatory drugs to slow periodontal disease progression. However, recently reported serious adverse effects preclude the use of cyclooxygenase-2 inhibitors as an adjunct to periodontal therapy. Adjunctive use of subantimicrobial dose doxycycline to non-surgical periodontal therapy is beneficial in the management of chronic periodontitis over 12 months. Controversial data exist on the effects of bisphosphonate administration as an adjunct to periodontal therapy. Evidence on modulation of other host mediators including lipoxins, cytokines and nitric oxide synthase is limited to animal research.

CONCLUSION

After validation in long-term clinical trials, adjunctive host modulation therapy may prove advantageous in the management of periodontal diseases.

Effects of Tempol, a membrane-permeable radical scavenger, in a rodent model periodontitis

BACKGROUND

Recent studies have demonstrated that Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl), a cell membrane-permeable radical scavenger, exerts protective effects in various models of inflammation and shock. Reactive oxygen species (ROS) plays a pivotal role in the induction of genes involved in physiological processes as well as in the response to inflammation.

AIM

We have investigated the effect of Tempol in a rat model of periodontitis.

MATERIALS AND METHODS

Periodontitis was induced in rats by placing a 2/0 braided silk ligature around the lower left first molar. At day 8, the gingivomucosal tissue encircling the mandibular first molar was removed for evaluation of neutrophils infiltration, tissue permeability, nitrotyrosine formation, poly-(ADP-ribose) polymerase (PARP) activation, radiography and histology.

RESULTS AND CONCLUSIONS

Legation significantly induced an increased neutrophil infiltration and a positive staining for nitrotyrosine formation and PARP activation. Ligation significantly increased Evans blue extravasation in gingivomucosal tissue and alveolar bone erosion as evaluated by radiography analysis. Intraperitonial injection of Tempol (10 mg/kg daily for 8 days) significantly decreased all of the parameters of inflammation as described above. This suggests that antioxidant therapies, which interfere with ROS, may be of benefit in the treatment of periodontitis.

Nitric oxide synthase inhibition prevents alveolar bone resorption in experimental periodontitis in rats

BACKGROUND

Periodontitis is the most frequent cause of tooth loss in adults. Nitric oxide (NO) has been linked to bone resorption mechanisms during inflammation processes. The aim of this study was to investigate the effect of NOS (NO synthase) inhibitors in the alveolar bone loss in an experimental periodontitis disease (EPD) model.

METHODS

Wistar rats were subjected to a ligature placement around the second upper left molars and were sacrificed at 11 days. Alveolar bone loss was evaluated by the sum of distances between the cusp tips and the alveolar bone along the axis of each molar root, subtracting from the contralateral side. Histopathological analysis was based on cell influx, alveolar bone, and cementum integrity. Leukogram was performed at 6 hours and 1, 7, and 11 days after the EPD induction. Groups were treated with the NOS inhibitors, aminoguanidine (AG) (2.5 to 10 mg/kg/d), or L-arginine methyl ester (L-NAME, 5 to 20 mg/kg/d) intraperitoneally (i.p.), 1 hour before the EPD induction and daily for 11 days. Controls received only saline (EPD group). As controls for L-NAME specificity, groups were co-treated with either L-arginine (150 to 600 mg/kg/d) or D-arginine (600 mg/kg/d) and L-NAME (20 mg/kg/d). Different groups were used for morphometric and histopathological analysis.

RESULTS

Both L-NAME and AG significantly and dose-dependently inhibited the alveolar bone loss as compared to EPD group. L-NAME (20 mg/kg/d) reduced the alveolar bone loss by 50%, whereas AG (5 mg/kg/d) reduced it by 47% compared to EPD. This result was coupled to a significant reduction of cell influx to the periodontium, as well as to the preservation of alveolar bone and cementum, seen at histopathology, for both compounds. The co-administration of L-arginine, but not of D-arginine reversed L-NAME effects.

CONCLUSION

These data provide evidence that NOS inhibitors prevent inflammatory bone resorption in experimental periodontitis.

Poly(ADP-ribose) polymerase activation by reactive nitrogen species--relevance for the pathogenesis of inflammation

Oxidative and nitrosative stress triggers DNA strand breakage, which then activates the nuclear enzyme poly(ADP-ribose) polymerase (PARP). Nitrogen-derived reactive oxidant species capable of involving DNA single strand breakage and PARP activation include peroxynitrite (the reaction product of nitric oxide and superoxide), but not nitric oxide per se. Activation of PARP may dramatically lower the intracellular concentration of its substrate, nicotinamide adenine dinucleotide, thus slowing the rate of glycolysis, electron transport, and subsequently ATP formation. This process can result in cell dysfunction and cell death. Here we review the role of reactive nitrogen species in the process of PARP activation, followed by the effect of pharmacological inhibition or genetic inactivation of PARP on the course of various forms of inflammation.