The use of locally delivered minocycline in the treatment of chronic periodontitis. A review of the literature

Comparison of Prophylactic Effects between Localized Biomimetic Minocycline and Systematic Amoxicillin on Implants Placed Immediately in Infected Sockets

This study evaluated the prophylactic effect of localized biomimetic minocycline and systemic amoxicillin on immediate implant placement at infected extraction sites. Twelve mongrels with six implants each were randomly assigned to five groups: uninfected negative control (Group N); infected with oral complex bacteria (Group P); infected and treated with amoxicillin one hour before implant placement (Group A); infected and treated with minocycline during implant placement (Group B); and infected and treated with amoxicillin one hour before implant placement and with minocycline during implant placement (Group C). Radiographic bone level, gingival index (GI), probing depth (PD), papillary bleeding index (PBI), and removal torque (RT) were recorded. There was no significant difference between Groups A, B, and C for bone loss. Group A showed the highest RT, the lowest PBI, and significantly lower GI and PD values than Group P. Group B exhibited significantly higher RT value than Group N and significantly smaller PD value than Group P at 6 w postoperatively. Localized minocycline could improve implant success by reducing bone loss and increasing RT and systemic amoxicillin could maintain the stability of the peri-implant soft tissue. However, combined use of these two antibiotics did not augment the prophylactic effect.

Electrosprayed minocycline hydrochloride-loaded microsphere/SAIB hybrid depot for periodontitis treatment

Minocycline hydrochloride (MINO) has been one of the most frequently used antibiotics in the treatment of periodontitis due to its antibacterial activity and osteogenesis effects; however, high levels of MINO administered during the treatment halt the formation of new bone. Therefore, the purpose of the present study was to prepare a MINO-microsphere/sucrose acetate isobutyrate (SAIB) hybrid depot to reduce the burst release of MINO and ensure antibacterial and osteogenesis effects of MINO in the treatment of periodontitis. Uniform microspheres, approximately 5 µm size, with a slightly rough surface and different MINO loading (10, 12, and 14%) were prepared, and the microspheres were added into SAIB, after which the burst release significantly decreased from 66.18 to 2.92%, from 71.82 to 3.82%, and from 73.35 to 4.45%, respectively, and the release from all the MINO-microspheres/SAIB hybrid depots lasted for 77 days. In addition, cytotoxicity test showed that the MINO-microsphere with 12% drug loading promoted the proliferation of osteoblasts the most and was subsequently used in vivo experiments. Moreover, in the model of ligatured-induced periodontitis in SD rats, the MINO-microsphere/SAIB hybrid depot not only significantly increased the alveolar bone height and bone volume but also reduced the inflammation of the periodontal tissue. Additionally, it also inhibited the expression of the receptor activator of nuclear factor-kappa B ligand (RANKL) and promoted the expression of osteoprotegerin (OPG).. These results indicated that the MINO-microsphere/SAIB hybrid depot might be promising in the treatment of periodontitis.

Minocycline-loaded PLGA electrospun membrane prevents alveolar bone loss in experimental peridontitis

Minocycline (MINO) is a tetracycline antibiotic effective against most of the bacteria microorganisms related to periodontal disease. Additionally, MINO promotes bone in vitro and in vivo. The objective of the present study was to establish the protocol for the preparation of MINO-loaded poly (lactic-co-glycolic acid) (MINO-PLGA) electrospun membranes and to evaluate their effect on osteogenesis in vitro and in a rat model of periodontitis. The characterization of MINO-PLGA electrospun membranes was assessed by scanning electron microscopy, laser scanning confocal microscopy, and contact angle measurement. The drug release study showed a sustained diffusion of MINO from electrospun membranes over a period of 40 d. The MINO-PLGA membranes containing 2% of the drug exhibited better support of osteoblast proliferation and adhesion and was subsequently used in vivo in an experimental periodontitis model. Its therapeutic potential was evaluated by the measurement of alveolar bone loss (ABL), bone volume analysis, histological analysis, and immunohistochemistry. MINO-PLGA membrane increased alveolar crest height in the periodontitis model, inhibited the expression of the ligand of the receptor activator for nuclear factor-κB (RANKL), and promoted the expression of its inhibitor, osteoprotegerin. The study demonstrated that MINO-PLGA electrospun membranes may be applied to stimulate bone regeneration in periodontitis.

Efficacy of Local Minocycline Agents in Treating Peri-Implantitis: An Experimental In Vivo Study in Beagle Dogs

BACKGROUND

Local delivery agents (LDA) have the advantage of delivering the antibiotics at high concentrations to the targeted sites. However, the constant flow of gingival crevicular fluids and saliva may restrict their efficacy. Therefore, the drug sustainability and pharmacodynamic properties of any proposed LDA should be evaluated.

METHODS

Four dental implants were placed unilaterally in the edentulous mandible of six beagle dogs. Peri-implantitis were experimentally induced using silk-ligatures. Each implant was randomly allocated to receive one of the following four treatments: (i) MC (Chitosan-alginate (CA) minocycline), (ii) MP (CA-without minocycline), (iii) PG (Polyacrylate-glycerin minocycline), and (iv) Control (mechanical debridement only). Mechanical therapies and LDAs were administered into the gingival sulcus two times at a 4-week interval. Drug sustainability as well as clinical, radiographical, and immunohistochemical (IHC) analyses were conducted to evaluate the efficacies of treatments.

RESULTS

Reduced mean probing depth was observed in all of the test groups after the second delivery. A minimal marginal bone level change was observed during the treatment period (MP (-0.06 ± 0.53 mm) to PG (-0.25 ± 0.42 mm)). The distribution of IHC cell marker analysis of all targeted antibodies ranged from 6.34% to 11.33%. All treatment outcomes between the test groups were comparable. A prolonged retention of LDA was observed from CA microspheres (MC and MP) at both administrations (p < 0.017) and prolonged sustainability of bacteriostatic effect was observed from MC compared to PG after the second administration (p < 0.05).

CONCLUSIONS

Prolonged retention of CA microspheres was observed and the longer bacteriostatic effect was observed from the MC group. Mechanical debridement with adjunct LDA therapy may impede peri-implantitis progression, however, prolonged drug action did not lead to improved treatment outcome.

Locally Applied Slow-Release of Minocycline Microspheres in the Treatment of Peri-Implant Mucositis: An Experimental In Vivo Study

BACKGROUND

The objective of this is preclinical investigation was to evaluate the differential drug sustainability and pharmacodynamic properties of two local minocycline microsphere carriers: chitosan-coated alginate (CA) and poly(meth)acrylate-glycerin (PG).

METHODS

Four dental implants were placed unilaterally in the edentulous mandible of six beagle dogs. Each implant was randomly assigned to receive one of the following four treatments: (i) CA (CA-based minocycline), (ii) placebo (CA substrate without minocycline), (iii) PG (PG-based minocycline) and (iv) control (mechanical debridement only). After inducing peri-implant mucositis, the randomly assigned treatments were administered into the gingival sulcus twice at a 4-week interval using a plastic-tipped syringe. Drug sustainability and pharmacodynamic (clinical, radiographical and cell marker intensity) evaluations were performed after each administration.

RESULTS

The CA microspheres remained longer around the healing abutment compared to the PG microspheres at both administrations and a longer bacteriostatic effect was observed from CA (7.0 ± 5.7 days) compared to PG (1.2 ± 2.6 days). The efficacy of the applied therapies based on clinical, radiographical and histological analyses were comparable across all treatment groups.

CONCLUSIONS

CA microspheres showed longer carrier and bacteriostatic effect sustainability when compared to PG microspheres, however, longer drug sustainability did not lead to improved treatment outcomes.

Locally delivered minocycline microspheres do not impair osseointegration of titanium implants in a rat femur model

BACKGROUND

The purpose of this study was to determine whether intramedullary administration of extended-release minocycline microspheres would affect osseointegration.

METHODS

Twenty-two rats were randomized to minocycline or saline femoral intramedullary injection followed by implantation of titanium alloy rods. Following euthanasia at four-weeks, pushout testing was performed and bone-volume-fraction assessed.

RESULTS

Pushout strength was marginally greater in minocycline-treated implants (122.5 ± 39.1 N) compared to saline (96.9 ± 26.1 N) (P = 0.098). No difference was observed in energy to maximum load, mean stiffness, or peri-implant bone-volume-fraction (P > 0.05).

CONCLUSIONS

Peri-implant minocycline administration did not impair implant fixation strength or peri-implant bone-volume, supporting its potential utility as an adjunct to intramedullary implants.

Commercial Local Pharmacotherapeutics and Adjunctive Agents for Nonsurgical Treatment of Periodontitis: A Contemporary Review of Clinical Efficacies and Challenges

Periodontal infections tend to be site-specific, mostly confined to the periodontal pocket. With the surge of antibiotic-resistant bacteria, the trend is shifting towards other therapeutic modalities, especially locally delivered approaches that include other pharmacotherapeutic drugs and medical devices. This narrative review aimed to provide insights into the clinical efficacy of local drug delivery and adjunctive agents used in nonsurgical management of periodontitis. Electronic (PubMed/MEDLINE, CENTRAL, and EMBASE) and bibliographic searches of past systematic reviews were carried out to identify previous publications on the topic. Only relevant literature and randomized controlled trials published in English were selected. In addition, a literature review was developed based on the selected articles. Experimental drugs or agents were excluded. This review highlights the clinically proven and commercially available therapeutic agents related to the management of periodontal disease with comparisons of their clinical efficacies and challenges. A vast array of commercial local pharmacotherapeutic agents had been clinically tested, but the methodologies and clinical results varied within and between each agent used, causing difficulty in drawing conclusions and providing support to the superiority of one agent over another. Considering the benefit-cost ratio with the modest clinical results, the long-term usefulness of these agents remains debatable.

Self-Assembly of DNA-Minocycline Complexes by Metal Ions with Controlled Drug Release

Here we reported a study of metal ions-assisted assembly of DNA-minocycline (MC) complexes and their potential application for controlling MC release. In the presence of divalent cations of magnesium or calcium ions (M²⁺), MC, a zwitterionic tetracycline analogue, was found to bind to phosphate groups of nucleic acids via an electrostatic bridge of phosphate (DNA)-M²⁺-MC. We investigated multiple parameters for affecting the formation of DNA-Mg²⁺-MC complex, including metal ion concentrations, base composition, DNA length, and single- versus double-stranded DNA. For different nitrogen bases, single-stranded poly(A)₂₀ and poly(T)₂₀ showed a higher MC entrapment efficiency of DNA-Mg²⁺-MC complex than poly(C)₂₀ and poly(G)₂₀. Single-stranded DNA was also found to form a more stable DNA-Mg²⁺-MC complex than double-stranded DNA. Between different divalent metal ions, we observed that the formation of DNA-Ca²⁺-MC complex was more stable and efficient than the formation of DNA-Mg²⁺-MC complex. Toward drug release, we used agarose gel to encapsulate DNA-Mg²⁺-MC complexes and monitored MC release. Some DNA-Mg²⁺-MC complexes could prolong MC release from agarose gel to more than 10 days as compared with the quick release of free MC from agarose gel in less than 1 day. The released MC from DNA-Mg²⁺-MC complexes retained the anti-inflammatory bioactivity to inhibit nitric oxide production from pro-inflammatory macrophages. The reported study of metal ion-assisted DNA-MC assembly not only increased our understanding of biochemical interactions between tetracycline molecules and nucleic acids but also contributed to the development of a highly tunable drug delivery system to mediate MC release for clinical applications.

Efficacy of Locally Administered 1.2% Rosuvastatin Gel in Patients with Periodontitis: A Randomized Placebo Controlled Clinical Trial

Objective Periodontitis initiation and progression are a result of host immune inflammatory response to oral pathogens. Several pharmacological agents are being delivered locally, to improve periodontal health. Hence, the present randomized placebo controlled clinical trial is designed to check the clinical and antimicrobial efficacy of locally delivered 1.2% rosuvastatin (RSV) in intrabony defects (IBD) in periodontitis patients.

Materials and Methods One-hundred patients were randomly allotted into two treatment groups: group A received 1. 2% RSV gel, scaling and root debridement and group B received placebo gel, scaling and root debridement. Clinical parameters, including modified sulcus bleeding index (mSBI), probing depth (PD), clinical attachment level (CAL), and plaque index (PI), were recorded at baseline before phase 1 and after 6 months. Radiographic assessment of IBD was done by cone beam computed tomography at baseline and after 6 months. Anaerobic colony count was done at baseline and after 180 days.

Results On intragroup comparison, there is a significant improvement in periodontal parameters in both the groups. On intergroup comparison, there is significant gain in CAL in group A than group B ( p = 0.04). There is significant decrease in PD in group A, compared to group B. There is significant bone fill in group A ( p = 0.034), compared to group B. With respect to mSBI, PI, and anaerobic colony count, there is no significant difference between the two groups after 6 months. No adverse effect was noticed in any subjects.

Conclusion The author concludes that 1.2% RSV gel when delivered locally into IBD improved periodontal clinical parameters such as PD and CAL and showed significant bone fill.

Assessment of clinical efficacy of locally delivered 0.2% Thymoquinone gel in the treatment of periodontitis

Objectives

To evaluate the potential benefits of local application of Thymoquinone gel as an adjunctive to scaling and root planing (SRP) in subjects with chronic periodontitis.

Material and methods

Twenty subjects with 40 test sites were selected according to inclusion and exclusion criteria. They were further divided into 2 groups. Group I comprised of study subjects (Thymoquinone in addition to SRP) and Group II comprised of control subjects (only SRP). Clinical parameters such as Plaque Index (PI), Gingival Index (GI), Probing Pocket Depth (PPD), Relative Attachment Level (RAL), were monitored at baseline and 6 weeks post operatively. Alkaline phosphatase (ALP) levels in gingival crevicular fluid (GCF) were evaluated at baseline and 6 weeks post operatively using microcapillaries. In addition antimicrobial efficacy of Thymoquinone was evaluated against 3 bacteria using antimicrobial strains.

Results

Statistically highly significant reduction was observed in PI, GI and PPD, rise in RAL and GCF ALP level in both the groups at 6 weeks from baseline. On comparison between Group I and Group II, former demonstrated statistically significant reduction in PPD, GCF-ALP levels and rise in RAL but statistically no significant differences were observed in PI and GI at 6 weeks. On microbiological assessment of 0.2% Thymoquinone gel, it was observed to be sensitive against P. gingivalis, A. actinomycetemcomitans and P. intermedia.

Conclusion

Significant changes in clinical and biochemical parameters were achieved in the current study. Hence, it is concluded that intracrevicular application of 0.2% Thymoquinone gel could be a beneficial adjunct to SRP in treating chronic periodontitis.

Metal ion-assisted self-assembly of complexes for controlled and sustained release of minocycline for biomedical applications

This study reports the development of novel drug delivery complexes self-assembled by divalent metal ion-assisted coacervation for controlled and sustained release of a hydrophilic small drug molecule minocycline hydrochloride (MH). MH is a multifaceted agent that has demonstrated therapeutic effects in infection, inflammation, tumor, as well as cardiovascular, renal, and neurological disorders due to its anti-microbial, anti-inflammatory, and cytoprotective properties. However, the inability to translate the high doses used in experimental animals to tolerable doses in human patients limits its clinical application. Localized delivery can potentially expose the diseased tissue to high concentrations of MH that systemic delivery cannot achieve, while minimizing the side effects from systemic exposure. The strong metal ion binding-assisted interaction enabled high drug entrapment and loading efficiency, and stable long term release for more than 71 d. Released MH demonstrated potent anti-biofilm, anti-inflammatory, and neuroprotective activities. Furthermore, MH release from the complexes is pH-sensitive as the chelation between minocycline and metal ions decreases with pH, allowing 'smart' drug release in response to the severity of pathology-induced tissue acidosis. This novel metal ion binding-mediated drug delivery mechanism can potentially be applied to other drugs that have high binding affinity for metal ions and may lead to the development of new delivery systems for a variety of drugs.

In situ forming implants for periodontitis treatment with improved adhesive properties

Novel in situ forming implants are presented showing a promising potential to overcome one of the major practical hurdles associated with local periodontitis treatment: limited adhesion to the surrounding tissue, resulting in accidental expulsion of at least parts of the implants from the patients' pockets. This leads to high uncertainties in the systems' residence times at the site of action and in the resulting drug exposure. In the present study, the addition of different types and amounts of plasticizers (acetyltributyl citrate and dibutyl sebacate) as well as of adhesive polymers (e.g., cellulose derivatives such as hydroxypropyl methylcellulose) is shown to allow for a significant increase in the stickiness of poly(lactic-co-glycolic acid)-based implants. The systems are formed in situ from N-methyl pyrrolidone-based liquid formulations. Importantly, at the same time, good plastic deformability of the implants can be provided and desired drug release patterns can be fine-tuned using several formulation tools. The antimicrobial activity of this new type of in situ forming implants, loaded with doxycycline hyclate, was demonstrated using the agar well diffusion method and multiple Streptococcus strains isolated from the oral microflora of patients suffering from periodontitis.

Comparative evaluation of locally delivered minocycline and metronidazole in the treatment of periodontitis

Objective:

The aim of this study was to evaluate and compare the efficacy of subgingivally delivered Minocycline microspheres and 25% Metronidazole gel when used as an adjunct to scaling and root planing (SRP) in the treatment of chronic periodontitis.

Materials and Methods:

A randomized, controlled, single center study was conducted involving 60 sites in 20 patients suffering from moderate to advanced chronic periodontitis. Each patient contributed three sites which were randomized to three treatment groups: SRP + insertion of Minocycline microspheres at day 1 (Group A), SRP + insertion of Metronidazole gel at day 1 and at day 7 (Group B), and SRP alone (Group C). Gingival index (GI), plaque index (PI), probing pocket depth (PPD), and clinical attachment level (CAL) were recorded at day 1, 1 month, and 3 months post therapy.

Results:

All treatments showed significant reductions in PPD and CAL at 1 and 3 months when compared to baseline values (P < 0.001). At 3 months, sites treated with minocycline showed an additional reduction in PPD of 0.85 ± 0.03 mm, significantly greater than SRP alone. Differences in mean PPD reduction between Group B and Group C and between Group A and Group B were not significant. At 3 months, difference in CAL gain between Group A and C was 0.50 ± 0.45, which was statistically significant and between Group B and C was 0.35 ± 0.11, which was not found to be statistically significant (P = 0.20). Differences in relative CAL between Group A and Group B were also not found to be statistically significant (P = 0.53).

Conclusion:

The results concluded that treatment with Minocycline microspheres and Metronidazole gel improve PPD and CAL in patients with periodontitis compared to SRP alone.

Minocycline hydrochloride nanoliposomes inhibit the production of TNF-α in LPS-stimulated macrophages

Background

As an adjunctive treatment of chronic periodontitis, it seems that the application of periocline or the other antimicrobials is effective against periodontopathogens. In this study, nanoliposomes were investigated as carriers of minocycline hydrochloride and the inhibition effects of minocycline hydrochloride nanoliposomes on the proliferation and lipopolysaccharide (LPS)-stimulated production of tumor necrosis factor-α (TNF-α) of macrophages were elucidated.

Methods

After stimulation with 10 μg/mL LPS, murine macrophages (ANA-1) were treated with 10, 20, 40, 50 and 70 μg/mL 2% minocycline hydrochloride nanoliposomes, minocycline hydrochloride solution, and periocline for 6, 12, 24, 48 and 60 hours, respectively. A tetrazolium (MTT) assay was used to evaluate macrophages cell proliferation rate and the levels of TNF-α mRNA were measured by SYBR Green Real Time PCR.

Results

Ten to 70 μg/mL 2% minocycline hydrochloride nanoliposomes, minocycline hydrochloride solution, and periocline showed dose- and time-dependent inhibition of ANA-1 proliferation. Minocycline hydrochloride nanoliposomes showed dose- and ratio-dependent inhibition of LPS-stimulated TNF-α secretion of ANA-1. The inhibition effect of 10 μg/mL minocycline hydrochloride nanoliposomes was significantly better than that of two positive control groups, and equated to that of 60 or 70 μg/mL periocline. The expression of TNF-α mRNA in experimental group continued to reduce linearly with time.

Conclusion

All three preparations of minocycline hydrochloride showed dose- and time-dependent inhibition of proliferation of ANA-1. Minocycline hydrochloride nanoliposomes have stronger and longer inhibition effect on LPS-stimulated TNF-α secretion of macrophages cell than minocycline hydrochloride solution and periocline.

Treatment modalities and evaluation models for periodontitis

Periodontitis is the most common localized dental inflammatory disease related with several pathological conditions like inflammation of gums (gingivitis), degeneration of periodontal ligament, dental cementum and alveolar bone loss. In this perspective, the various preventive and treatment modalities, including oral hygiene, gingival irrigations, mechanical instrumentation, full mouth disinfection, host modulation and antimicrobial therapy, which are used either as adjunctive treatments or as stand-alone therapies in the non-surgical management of periodontal infections, have been discussed. Intra-pocket, sustained release systems have emerged as a novel paradigm for the future research. In this article, special consideration is given to different locally delivered anti-microbial and anti inflammatory medications which are either commercially available or are currently under consideration for Food and Drug Administration (FDA) approval. The various in vitro dissolution models and microbiological strain investigated to impersonate the infected and inflamed periodontal cavity and to predict the in vivo performance of treatment modalities have also been thrashed out. Animal models that have been employed to explore the pathology at the different stages of periodontitis and to evaluate its treatment modalities are enlightened in this proposed review.

Cytoprotective activity of minocycline includes improvement of mitochondrial coupling: the importance of minocycline concentration and the presence of VDAC

Available data indicate that minocycline, an antibiotic of the tetracycline family, has cytoprotective properties due to a direct interaction with mitochondria. Yet, the data in the case of isolated mitochondria suggest discrepant or even detrimental effect(s) of the interaction. We have studied the cytoprotective activity displayed by minocycline in the case of the yeast Saccharomyces cerevisiae cells pretreated with H₂O₂. We demonstrated that the activity of minocycline required the presence of VDAC (voltage-dependent anion-selective channel) and provided distinct improvement of mitochondrial coupling. In the case of isolated mitochondria, we verified that minocycline exhibited uncoupler activity when applied in micromolar concentrations. However, when added in nanomolar concentrations, minocycline was able to improve the level of coupling for isolated mitochondria. The coupling improvement effect was observed in mitochondria containing VDAC but not in Δpor1 mitochondria (depleted of VDAC1, termed here VDAC) and in both types of mitoplasts. Thus, properly low concentrations of minocycline within the cell in the vicinity of VDAC-containing mitochondria enable the improvement of energy coupling of mitochondria that contributes to cytoprotective activity of minocycline.

Improved drug loading and antibacterial activity of minocycline-loaded PLGA nanoparticles prepared by solid/oil/water ion pairing method

Background

Low drug entrapment efficiency of hydrophilic drugs into poly(lactic-co-glycolic acid) (PLGA) nanoparticles is a major drawback. The objective of this work was to investigate different methods of producing PLGA nanoparticles containing minocycline, a drug suitable for periodontal infections.

Methods

Different methods, such as single and double solvent evaporation emulsion, ion pairing, and nanoprecipitation were used to prepare both PLGA and PEGylated PLGA nanoparticles. The resulting nanoparticles were analyzed for their morphology, particle size and size distribution, drug loading and entrapment efficiency, thermal properties, and antibacterial activity.

Results

The nanoparticles prepared in this study were spherical, with an average particle size of 85–424 nm. The entrapment efficiency of the nanoparticles prepared using different methods was as follows: solid/oil/water ion pairing (29.9%) > oil/oil (5.5%) > water/oil/water (4.7%) > modified oil/water (4.1%) > nano precipitation (0.8%). Addition of dextran sulfate as an ion pairing agent, acting as an ionic spacer between PEGylated PLGA and minocycline, decreased the water solubility of minocycline, hence increasing the drug entrapment efficiency. Entrapment efficiency was also increased when low molecular weight PLGA and high molecular weight dextran sulfate was used. Drug release studies performed in phosphate buffer at pH 7.4 indicated slow release of minocycline from 3 days to several weeks. On antibacterial analysis, the minimum inhibitory concentration and minimum bactericidal concentration of nanoparticles was at least two times lower than that of the free drug.

Conclusion

Novel minocycline-PEGylated PLGA nanoparticles prepared by the ion pairing method had the best drug loading and entrapment efficiency compared with other prepared nanoparticles. They also showed higher in vitro antibacterial activity than the free drug.

Minocycline exerts uncoupling and inhibiting effects on mitochondrial respiration through adenine nucleotide translocase inhibition

The present study was aimed to provide a better understanding of the mitochondria-targeted actions of minocycline (MC), a second-generation tetracycline which has cytoprotective effects. Although the specific mechanisms underlying its activity remained elusive, considerable amounts of data indicated mitochondria as the primary pharmacological target of MC. Previous reports have shown that MC affects the oxygen-uptake rate by isolated mitochondria in different respiratory states. Here, we report on the effect of MC, in the range 50-200μM, on mitochondrial respiration. State 3 respiration titration with carboxyatractyloside revealed that MC inhibits the adenine nucleotide translocase. Furthermore, we analyze MC channel-forming capacity in the lipid membrane bilayer. Our results confirmed the crucial role of Δψ and showed a dependence on Ca(2+) for MC to have an effect on mitochondria. Our data also indicated that outer and inner mitochondrial membranes contribute differently to this effect, involving the presence of Δψ (the inner membrane) and VDAC (the outer membrane). Data from three isosmotic media indicate that MC does not increase the permeability of the inner membrane to protons or potassium. In addition, by using mitoplasts and ruthenium red, we showed that Ca(2+) uptake is not involved in the MC effect, suggesting involvement of VDAC in the MC interaction with the outer membrane. Our data contribute to unravel the mechanisms behind the mitochondria-targeted activity of the cytoprotective drug MC.

Impairment of mitochondrial function by minocycline

There is an ongoing debate on the presence of beneficial effects of minocycline (MC), a tetracycline-like antibiotic, on the preservation of mitochondrial functions under conditions promoting mitochondria-mediated apoptosis. Here, we present a multiparameter study on the effects of MC on isolated rat liver mitochondria (RLM) suspended either in a KCl-based or in a sucrose-based medium. We found that the incubation medium used strongly affects the response of RLM to MC. In KCl-based medium, but not in sucrose-based medium, MC triggered mitochondrial swelling and cytochrome c release. MC-dependent swelling was associated with mitochondrial depolarization and a decrease in state 3 as well as uncoupled respiration. Swelling of RLM in KCl-based medium indicates that MC permeabilizes the inner mitochondrial membrane (IMM) to K(+) and Cl(-). This view is supported by our findings that MC-induced swelling in the KCl-based medium was partly suppressed by N,N'-dicyclohexylcarbodiimide (an inhibitor of IMM-linked K(+)-transport) and tributyltin (an inhibitor of the inner membrane anion channel) and that swelling was less pronounced when RLM were suspended in choline chloride-based medium. In addition, we observed a rapid MC-induced depletion of endogenous Mg(2+) from RLM, an event that is known to activate ion-conducting pathways within the IMM. Moreover, MC abolished the Ca(2+) retention capacity of RLM irrespective of the incubation medium used, most likely by triggering permeability transition. In summary, we found that MC at low micromolar concentrations impairs several energy-dependent functions of mitochondria in vitro.

Supportive periodontal therapy using mechanical instrumentation or 2% minocycline gel: a 12 month randomized, controlled, single masked pilot study

OBJECTIVE

To compare the short-term performance of subgingival local delivery of 2% minocycline gel and conventional subgingival debridement in supportive periodontal therapy (SPT) patients.

METHODS

Forty adult patients having completed active treatment for moderate to advanced chronic periodontitis were included in a randomized, controlled, single masked maintenance care pilot study. Sites with residual pocket probing depths > or =5 mm and bleeding on probing were treated with either minocycline gel (minocycline-group) or scaling and root planing only (debridement-group) at baseline, 3, 6, and 9 months. Clinical and microbiological examinations were performed at baseline, 3, 6, 9, and 12 months.

RESULTS

Full-mouth plaque and bleeding scores remained <10% and <20%, respectively, for both groups throughout the study. In both groups there was a persistent reduction in number of teeth and sites with probing pocket depths > or =5 mm (p<0.05) with no significant differences between the groups. The prevalence of Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Prevotella nigrescens, remained at levels < or =10(5) in the majority of patients and sites in both groups.

CONCLUSION

This pilot study failed to show a difference between local delivery of 2% minocycline gel as mono-therapy and traditional subgingival debridement in patients on SPT.

Efficacy of subgingivally applied minocycline in the treatment of chronic periodontitis

BACKGROUND

The use of adjunctive minocycline with mechanical debridement in treating periodontitis has been widely studied using different methods. However, the results from these studies are equivocal.

OBJECTIVE

The purpose of this study was to clarify the efficacy of the adjunctive use of subgingival minocycline application plus scaling/root planing as compared with the results of one episode of scaling/root planing in the treatment of chronic periodontitis.

METHODS

Fifteen patients were enrolled in this split-mouth clinical trial. Probing depth, clinical attachment loss, gingival index, and bleeding on probing were evaluated at the baseline before scaling/root planing and 6, 10, 14, and 18 weeks later according to a single-blind protocol. The amount of interleukin-1beta (interleukin-1beta pg/site) at each lesion was also simultaneously measured in gingival crevicular fluid in a parallel comparison design. After full-mouth baseline measurements and scaling/root planing, 78 lesions with a residual mean probing depth of 5 mm at anterior teeth were selected and equally distributed in either right or left sites based on a split-mouth symmetrical design and randomly assigned to one of two treatment groups (with or without minocycline administration, n = 39 for each group).

RESULTS

Probing depth significantly decreased from the baseline (week 0) to week 6 after scaling/root planing (p < 0.05) in both groups, but there was no statistically significant difference between the two groups (p > 0.05). However, at weeks 10, 14, and 18, the experimental group showed significantly greater improvement in pocket reduction than the control group (p < 0.05). Similarly, both groups also showed significant decreases in gingival index scores from weeks 0-6 (p < 0.05), but gingival index reductions at weeks 10, 14, and 18 were statistically significant in favor of the experimental group (p < 0.05). The experimental group had more attachment gain than the control group at weeks 14 and 18 (p < 0.05). Values of interleukin-1beta (pg/site) at the experimental sites were significantly reduced at weeks 10, 14, and 18, as compared to values at control sites (p < 0.01). Finally, the incidence of bleeding on probing showed no differences between the two groups for any time interval (p > 0.05).

CONCLUSIONS

In this 18-week clinical trial, the results suggested that scaling/root planing with adjunctive subgingival administration of minocycline ointment has a significantly better and prolonged effect compared to scaling/root planing alone on the reduction of probing depth, clinical attachment loss, gingival index, and interleukin-1beta content, but not on bleeding on probing.

Microflora cultivable from minocycline strips placed in persisting periodontal pockets

OBJECTIVE

The microflora that develops on minocycline strips, used as an adjunct in non-surgical periodontal therapy was studied.

DESIGN AND METHODS

Minocycline (1.4 mg in polycaprolactone vehicle) and control strips were applied into all residual pockets (PD > or = 5mm, > or =2 pockets/subject) of patients with chronic periodontitis 1 month after a course of non-surgical periodontal therapy. Strips were inserted and retained for 3 days, changed to new strips for 3 more days and then removed. Strips were recovered from 14 (eight test, six control) of the 34 participants at day 0 (strip inserted, left for 30 s, removed), days 3 and 6, for (i) anaerobic culture, (ii) coliforms culture, using MacConkey agar, (iii) yeast culture, using Sabouraud's dextrose agar.

RESULTS

The mean anaerobic cfu/strip (x10(5); control/test) were 2/6, 24/2, 11/2 at days 0, 3 and 6, respectively (P > 0.05). The corresponding mean proportion of Gram-negative rods and fusiforms were 27%/21%, 27%/15% and 55%/8%. The proportions of Gram-negative rods on test strips by day 6 were significantly reduced (P < 0.05). A significantly increased prevalence of Streptococcus mitis biovar 1 was found on spent test strips (control versus test; 0% versus 38%, Fisher exact test, P = 0.01). Coliform prevalence at days 0, 3 and 6 on control/test strips were 0/13%, 50%/38% and 50%/13%. Yeasts were occasionally isolated.

CONCLUSIONS

The findings indicated that the minocycline strips but not the control strip supported a microbial colonisation compatible with periodontal health by day 6.

The Potential of Minocycline for Neuroprotection in Human Neurologic Disease

Minocycline is a member of the tetracycline class of molecules with broad-spectrum antibiotic activity. The unique properties of minocycline result in increased tissue distribution when compared with the other tetracyclines. Of particular interest is the ability of minocycline to diffuse into the central nervous system at clinically effective levels. Aside from its antimicrobial properties, minocycline has been found to have beneficial effects on inflammation, microglial activation, matrix metalloproteinases, nitric oxide production, and apoptotic cell death. Concordantly, minocycline has been found to have neuroprotective effects in animal models of a number of diseases including stroke, multiple sclerosis, and Parkinson disease. The proven safety of minocycline over decades of use as an antibiotic suggests that it may have potential for development into an effective treatment of multiple neurologic conditions in humans.

Probing depth changes following 2 years of periodontal maintenance therapy including adjunctive controlled release of chlorhexidine

BACKGROUND

Multicenter clinical trials have established that the adjunctive use of the subgingival controlled release of chlorhexidine, (CHX chip), significantly reduces probing depth (PD), improves clinical attachment levels, and reduces bleeding on probing compared to scaling and root planing (SRP) alone for periods of up to 9 months. The present report is based on a phase IV clinical trial to examine the adjunctive use of the CHX chip for routine periodontal maintenance therapy (RPMT) over 2 years.

METHODS

Eight hundred thirty-five (835) patients were recruited into the study. At baseline a CHX chip was placed in pocket sites with PD > or = 5 mm. The patients were scheduled to receive RPMT at 3-month intervals with repeated CHX chip placement at sites where the PD remained > or = 5 mm. Patients who did not attend the 24-month recall visit or who failed to attend 2 consecutive time frame examinations were excluded from the analyses.

RESULTS

The 595 patients included showed a continuous decrease in PD over 2 years of 0.95 mm. After 2 years, 23.2% of patients had at least 2 pockets showing a reduction in PD of 2 mm or more and 58.9% of the sites had been reduced to a PD of < 5 mm. Only 2.9% (n = 57) of the sites showed an increase in PD of > or = 2 mm. Adverse events were mild to moderate in nature and resolved spontaneously without medication.

CONCLUSION

The results of this Phase IV or follow-up trial indicate that the adjunctive use of the CHX chip is a clinically safe and effective treatment option for long-term management of chronic periodontitis.

Clinical periodontal findings and microflora profiles in children with chronic neutropenia under supervised oral hygiene

BACKGROUND

This is the first known case report that used a polymerase chain reaction (PCR)-based method to help identify the oral microflora in patients with chronic neutropenia. In this study, we report clinical periodontal findings and microflora profiles of 2 children, 1 with severe congenital neutropenia (SCN, Kostmann type) and 1 with cyclic neutropenia (CN).

METHODS

The SCN patient had severe gingivitis, whereas the patient with CN had mild gingivitis in the gingival margins. Monthly oral cleaning instruction and review were performed without subsequent periodontal therapy. Oral hygiene conditions remained satisfactory and visible plaque was scarce, despite the persistence of mild gingivitis. Under supervised oral hygiene, we examined the presence of periodontal pathogens from patient plaque samples.

RESULTS

By a PCR-based method, Prevotella nigrescens, Bacteroides forsythus, Campylobacter rectus, and Capnocytophaga gingivalis were detected in the SCN patient and P. intermedia, C. rectus, C. gingivalis, and C. sputigena in the CN patient, suggesting the existence of periodontal pathogens. Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Treponema denticola, and C. ochracea were not found in either patient.

CONCLUSIONS

Use of 1% povidone iodine solution and local antibiotic application under supervised oral hygiene were helpful to improve gingival conditions in patients with chronic neutropenia.

Measurement of peptidase activity and evaluation of effectiveness of administration of minocycline for treatment of dogs with periodontitis

OBJECTIVE

To determine clinical, enzymatic, and microbiologic effects of controlled-release localized administration of minocycline on dogs with periodontitis.

ANIMALS

Five adult Beagles with periodontitis.

PROCEDURE

After tooth scaling and root planing, 2 treatment, 1 placebo, and 1 control site were selected for each dog. Treatment sites (n = 10) received a periodontal formulation of minocycline hydrochloride, placebo sites (5) received ointment without minocycline, and control sites (5) did not receive ointment. Treatments were administered 4 times at weekly intervals. Peptidase activity and clinical and microbiologic effects were evaluated and compared among sites for 17 weeks.

RESULTS

Bleeding of the gums on probing (BOP) and pocket depth (PD) improved at the treatment site and were maintained for 13 weeks after treatment. However, BOP and PD in placebo and control sites increased from weeks 9 to 17 Peptidase activity in the periodontal pocket decreased noticeably from week 1 to 17, compared with baseline values for the treatment site. However, peptidase activity for placebo and control sites increased and were above baseline values on week 9 and week 13, respectively. Total bacterial counts decreased by 90% for treatment sites and remained at that value for 13 weeks. However, for placebo and control sites, bacterial counts increased and reached the baseline value on week 17.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased peptidase activity is correlated with the progression of periodontitis in dogs. Treatment with minocycline, using a localized delivery system, was effective in dogs for at least 13 weeks after cessation of drug administration.