In vitro sensitivity of the three mammalian collagenases to tetracycline inhibition: relationship to bone and cartilage degradation

Identification of allosteric fingerprints of alpha-synuclein aggregates in matrix metalloprotease-1 and substrate-specific virtual screening with single molecule insights

Alpha-synuclein (aSyn) has implications in pathological protein aggregations in neurodegeneration. Matrix metalloproteases (MMPs) are broad-spectrum proteases and cleave aSyn, leading to aggregation. Previous reports showed that allosteric communications between the two domains of MMP1 on collagen fibril and fibrin depend on substrates, activity, and ligands. This paper reports quantification of allostery using single molecule measurements of MMP1 dynamics on aSyn-induced aggregates by calculating Forster Resonance Energy Transfer (FRET) between two dyes attached to the catalytic and hemopexin domains of MMP1. The two domains of MMP1 prefer open conformations that are inhibited by a single point mutation E219Q of MMP1 and tetracycline, an MMP inhibitor. A two-state Poisson process describes the interdomain dynamics, where the two states and kinetic rates of interconversion between them are obtained from histograms and autocorrelations of FRET values. Since a crystal structure of aSyn-bound MMP1 is unavailable, binding poses were predicted by molecular docking of MMP1 with aSyn using ClusPro. MMP1 dynamics were simulated using predicted binding poses and compared with the experimental interdomain dynamics to identify an appropriate pose. The selected aSyn-MMP1 binding pose near aSyn residue K45 was simulated and analyzed to define conformational changes at the catalytic site. Allosteric residues in aSyn-bound MMP1 exhibiting strong correlations with the catalytic motif residues were compared with allosteric residues in free MMP1, and aSyn-specific residues were identified. The allosteric residues in aSyn-bound MMP1 are K281, T283, G292, G327, L328, E329, R337, F343, G345, N346, Y348, G353, Q354, D363, Y365, S366, S367, F368, P371, R372, V374, K375, A379, F391, A394, R399, M414, F419, V426, and C466. Shannon entropy was defined to quantify MMP1 dynamics. Virtual screening was performed against a site on selected aSyn-MMP1 binding poses, which showed that lead molecules differ between free MMP1 and substrate-bound MMP1. Also, identifying aSyn-specific allosteric residues in MMP1 enabled further selection of lead molecules. In other words, virtual screening needs to take substrates into account for potential substrate-specific control of MMP1 activity in the future. Molecular understanding of interactions between MMP1 and aSyn-induced aggregates may open up the possibility of degrading aggregates by targeting MMPs.

Allosteric Communications between Domains Modulate the Activity of Matrix Metalloprotease-1

An understanding of the structure-dynamics relationship is essential for understanding how a protein works. Prior research has shown that the activity of a protein correlates with intradomain dynamics occurring at picosecond to millisecond timescales. However, the correlation between interdomain dynamics and the function of a protein is poorly understood. Here, we show that communications between the catalytic and hemopexin domains of matrix metalloprotease-1 (MMP1) on type 1 collagen fibrils correlate with its activity. Using single-molecule Förster resonance energy transfer, we identified functionally relevant open conformations in which the two MMP1 domains are well separated, which were significantly absent for catalytically inactive point mutant (E219Q) of MMP1 and could be modulated by an inhibitor or an enhancer of activity. The observed relevance of open conformations resolves the debate about the roles of open and closed MMP1 structures in function. We fitted the histograms of single-molecule Förster resonance energy transfer values to a sum of two Gaussians and the autocorrelations to an exponential and power law. We used a two-state Poisson process to describe the dynamics and calculate the kinetic rates from the fit parameters. All-atom and coarse-grained simulations reproduced some of the experimental features and revealed substrate-dependent MMP1 dynamics. Our results suggest that an interdomain separation facilitates opening up the catalytic pocket so that the collagen chains come closer to the MMP1 active site. Coordination of functional conformations at different parts of MMP1 occurs via allosteric communications that can take place via interactions mediated by collagen even if the linker between the domains is absent. Modeling dynamics as a Poisson process enables connecting the picosecond timescales of molecular dynamics simulations with the millisecond timescales of single-molecule measurements. Water-soluble MMP1 interacting with water-insoluble collagen fibrils poses challenges for biochemical studies that the single-molecule tracking can overcome for other insoluble substrates. Interdomain communications are likely important for multidomain proteins.

The Role of Matrix Metalloproteinases in Periodontal Disease

This review provides a detailed description of matrix metalloproteinases (MMPs), focusing on those that are known to have critical roles in bone and periodontal disease. Periodontal disease is an inflammatory process initiated by anaerobic bacteria, which promote the host immune response in the form of a complex network of molecular pathways involving proinflammatory mediators such as cytokines, growth factors, and MMPs. MMPs are a family of 23 endopeptidases, collectively capable of degrading virtually all extracellular matrix (ECM) components. This study critically discusses the available research concerning the involvement of the MMPs in periodontal disease development and progression and presents possible therapeutic strategies. MMPs participate in morphogenesis, physiological tissue turnover, and pathological tissue destruction. Alterations in the regulation of MMP activity are implicated in the manifestation of oral diseases, and MMPs comprise the most important pathway in tissue destruction associated with periodontal disease. MMPs can be considered a risk factor for periodontal disease, and measurements of MMP levels may be useful markers for early detection of periodontitis and as a tool to assess prognostic follow-ups. Detection and inhibition of MMPs could, therefore, be useful in periodontal disease prevention or be an essential part of periodontal disease therapy, which, considering the huge incidence of the disease, may greatly improve oral health globally.

Review of Three New Agents that Target Angiogenesis, Matrix Metalloproteinases, and Cyclin-Dependent Kinases

Background

Many potential new antineoplastic agents are currently in various stages of clinical development. Three areas of drug development include antiangiogenic compounds, agents that inhibit matrix metalloproteinases, and agents that modulate cyclin-dependent kinases.

Methods

The authors reviewed the available data for endostatin, COL-3, and flavopiridol, each of which is being developed with one of the above-mentioned proposed mechanisms of action. These agents are among the first drugs to reach clinical testing that is focusing on these novel targets.

Results

Endostatin has finished preclinical testing and the first human trials are about to be initiated. COL-3 is in phase I testing in several locations. Phase I studies for flavopiridol have been completed and several phase II studies are underway. It is unknown at this point if any of these agents will provide clinical benefit to patients at doses that do not cause unacceptable toxicity.

Conclusions

These agents are currently at various stages of clinical testing. Albeit promising as potential modulators in molecular and biochemical pathways, continued research is needed into the toxicities and clinical usefulness of these agents.

Doxycycline as an anti-inflammatory agent: updates in dermatology

Doxycycline, a tetracycline antibiotic, is widely used in the field of dermatology for its antibiotic properties, anti-inflammatory properties and good safety profile. Over the past decades, numerous studies have clarified some of the anti-inflammatory mechanisms of doxycycline. In this review article, we aimed to provide an update on recent data on the anti-inflammatory properties of doxycycline and its potential role in cutaneous inflammatory diseases. Better understanding of these mechanisms might offer the practicing clinicians a better use of this therapeutic tool. In addition, research in this field could help clarify pathogenic aspects of inflammatory dermatologic diseases responsive to this medication. Further research is needed to fully elucidate the potential of doxycycline as an anti-inflammatory agent, and the development of new topical vehicles could open ways to new therapeutic possibilities for dermatologists.

Accelerated degradation of collagen membranes in diabetic rats is associated with increased infiltration of macrophages and blood vessels

OBJECTIVES

Increased collagenolytic activity in diabetes may compromise collagen membrane (CM) survival. Tetracycline (TTC) possesses anti-collagenolytic properties and delays CM degradation. This study evaluated macrophage and capillary infiltration within CMs in diabetic rats.

MATERIALS AND METHODS

Diabetes was induced in 20 Wistar rats by streptozotocin and 20 served as controls. Biotin-labeled CM discs were immersed in either TTC (50 mg/ml) or PBS. In each animal, 2 discs (TTC and control) were implanted under the parietal periosteum and rats were sacrificed at 2 or 4 weeks post-implantation. The area and thickness of the residual disc collagen were measured following staining with streptavidin, and the number of macrophages and blood vessels within the membranes was determined using specific antibodies (to CD68 and transglutaminase II, respectively).

RESULTS

Diabetes significantly reduced the area and thickness of the CMs, while TTC increased CM thickness significantly in both groups of rats at 2 and 4 weeks. Diabetes increased the number of macrophages (∼eightfold at 2 weeks and ∼fourfold at 4 weeks), but TTC had no significant effect. Finally, diabetes increased the number of blood vessels within the discs (∼threefold at 2 weeks and ∼twofold at 4 weeks), while TTC had no effect.

CONCLUSIONS

Diabetes increases degradation of native CMs and the number of blood vessels and macrophages within them. TTC immersion delays CM degradation without an apparent effect on macrophage and blood vessel penetration.

CLINICAL RELEVANCE

Enhanced CM degradation in diabetic conditions which impair guided regenerative procedure outcome is apparently related to increased blood vessel formation and macrophage infiltration.

COL-3, a chemically modified tetracycline, inhibits lipopolysaccharide-induced microglia activation and cytokine expression in the brain

Microglia activation results in release of proinflammatory molecules including cytokines, which contribute to neuronal damage in the central nervous system (CNS) if not controlled. Tetracycline antibiotics such as minocycline inhibit microglial activation and cytokine expression during CNS inflammation. In the present study we found that administration of chemically modified tetracycline-3 (COL-3), inhibits lipopolysaccharide (LPS)-induced microglial and p38 MAPK activation, as well as the increase in TNF-α, but not IL-1β expression, in the brains of BALB/c mice. COL-3 has been described to have no antibacterial activity. We observed that COL-3 had no activity against a Gram-negative bacteria, Escherichia coli; however surprisingly, COL-3 had antibacterial activity against a Gram-positive bacteria Staphylococcus aureus, with a minimum inhibitory concentration of 1 mg/ml. Our data show that COL-3 has some antibacterial activity against S. aureus, inhibits LPS-induced neuroinflammation, and displays potential as a therapeutic agent for treatment of conditions involving CNS inflammation.

Metalloproteinases and their associated genes contribute to the functional integrity and noise-induced damage in the cochlear sensory epithelium

Matrix metalloproteinases (MMPs) and their related gene products regulate essential cellular functions. An imbalance in MMPs has been implicated in various neurological disorders, including traumatic injuries. Here, we report a role for MMPs and their related gene products in the modulation of cochlear responses to acoustic trauma in rats. The normal cochlea was shown to be enriched in MMP enzymatic activity, and this activity was reduced in a time-dependent manner after traumatic noise injury. The analysis of gene expression by RNA sequencing and qRT-PCR revealed the differential expression of MMPs and their related genes between functionally specialized regions of the sensory epithelium. The expression of these genes was dynamically regulated between the acute and chronic phases of noise-induced hearing loss. Moreover, noise-induced expression changes in two endogenous MMP inhibitors, Timp1 and Timp2, in sensory cells were dependent on the stage of nuclear condensation, suggesting a specific role for MMP activity in sensory cell apoptosis. A short-term application of doxycycline, a broad-spectrum inhibitor of MMPs, before noise exposure reduced noise-induced hearing loss and sensory cell death. In contrast, a 7 d treatment compromised hearing sensitivity and potentiated noise-induced hearing loss. This detrimental effect of the long-term inhibition of MMPs on noise-induced hearing loss was further confirmed using targeted Mmp7 knock-out mice. Together, these observations suggest that MMPs and their related genes participate in the regulation of cochlear responses to acoustic overstimulation and that the modulation of MMP activity can serve as a novel therapeutic target for the reduction of noise-induced cochlear damage.

Matrix metalloproteinase inhibitor COL-3 prevents the development of paclitaxel-induced hyperalgesia in mice

OBJECTIVE

To study the potential of chemically modified tetracycline-3 (COL-3), a potent matrix metalloproteinase (MMP) inhibitor, to protect against the development of paclitaxel-induced painful neuropathy and its immunomodulatory effects.

MATERIALS AND METHODS

The reaction latency to thermal stimuli (hot plate test) of female BALB/c mice was recorded before and after treatment with paclitaxel (2 mg/kg i.p.), paclitaxel plus COL-3 (4, 20 or 40 mg/kg p.o.) or their vehicles for 5 consecutive days. Gene transcripts of CD11b (marker for microglia), 5 cytokines (IFN-γ, IL-1β, IL-6, IL-10 and TNF-α) and 3 chemokines (CCL2, CXCL10 and CX3CL1) were quantified by real-time PCR in the brains, spinal cords and spleens of mice sacrificed on day 7 after treatment.

RESULTS

Treatment with paclitaxel reduced the reaction latency time to thermal stimuli (thermal hyperalgesia) for 4 weeks, with maximum effect on days 7 and 10. The coadministration of paclitaxel with COL-3 40 mg/kg, but not lower doses, prevented the development of paclitaxel-induced thermal hyperalgesia. Treatment with paclitaxel alone or coadministration with COL-3 increased CD11b transcript levels in the brain but not in the spinal cord. Treatment with paclitaxel reduced IL-6 transcript levels in the spinal cord but did not alter the transcript levels of other cytokines or chemokines in the brain, spinal cord or spleen. The coadministration of COL-3 with paclitaxel significantly increased the transcript levels of IL-6 in the spleen and decreased CX3CL1 transcripts in the brain in comparison to treatment with paclitaxel alone.

CONCLUSION

Our results indicate that the MMP inhibitor COL-3 protected against paclitaxel-induced thermal hyperalgesia and, thus, could be useful in the prevention of chemotherapy-induced painful neuropathy.

Opposing effects of diabetes and tetracycline on the degradation of collagen membranes in rats

BACKGROUND

Increased collagenolytic activity, characteristic of uncontrolled diabetes, may compromise collagen membrane (CM) survival. Tetracycline (TCN) possesses anticollagenolytic properties and delays CM degradation in healthy animals. This study evaluates the degradation of TCN--immersed and -non-immersed CMs in rats with diabetes compared to those with normoglycemia.

METHODS

Diabetes was induced in 15 12-week-old male Wistar rats by injection of 65 mg/kg streptozotocin. The control group consisted of 15 rats with normoglycemia. Sixty bilayered CM disks were labeled before implantation with aminohexanoyl-biotin-N-hydroxy-succinimide ester, of which 30 were immersed in 50 mg/mL TCN solution (experimental) or phosphate-buffered saline (PBS) (control). In each animal, two disks (control and experimental) were implanted in two midsagittal calvarial defects in the parietal bone. Similar non-implanted disks served as baseline. After 3 weeks, animals were euthanized, and the calvaria and overlying soft tissues were processed for demineralized histologic analysis. Horseradish peroxidase-conjugated streptavidin was used to detect the biotinylated collagen. The area of residual collagen within the membrane disks was measured and analyzed with a digital image analysis system. Several slides from each specimen were also stained with hematoxylin and eosin. Statistical analysis consisted of paired and unpaired t tests.

RESULTS

The amount of residual collagen in PBS-immersed disks was lower in rats with diabetes compared to rats with normoglycemia (69% of baseline versus 93%, respectively, P <0.001). TCN immersion increased the amount of residual collagen contents in both diabetic (83% of baseline) and healthy (97.5% of baseline) animals (P <0.0001).

CONCLUSION

Diabetes increases CM degradation, whereas immersion in 50 mg/mL TCN solution before implantation presents an opposite effect.

Tetracycline compounds with non-antimicrobial organ protective properties: possible mechanisms of action

Tetracyclines were developed as a result of the screening of soil samples for antibiotics. The first(t) of these compounds, chlortetracycline, was introduced in 1947. Tetracyclines were found to be highly effective against various pathogens including rickettsiae, as well as both gram-positive and gram-negative bacteria, thus becoming the first class of broad-spectrum antibiotics. Many other interesting properties, unrelated to their antibiotic activity, have been identified for tetracyclines which have led to widely divergent experimental and clinical uses. For example, tetracyclines are also an effective anti-malarial drug. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Another tetracycline, doxycycline is known to exert anti-protease activities. Doxycycline can inhibit matrix metalloproteinases which contribute to tissue destruction activities in diseases such as periodontitis. A large body of literature has provided additional evidence for the "beneficial" actions of tetracyclines, including their ability to act as reactive oxygen species scavengers and anti-inflammatory agents. This review provides a summary of tetracycline's multiple mechanisms of action as a means to understand their beneficial effects.

Tetracyclines: a pleitropic family of compounds with promising therapeutic properties. Review of the literature

There must be something unique about a class of drugs (discovered and developed in the mid-1940s) where there are more than 130 ongoing clinical trials currently listed. Tetracyclines were developed as a result of the screening of soil samples for antibiotic organisms. The first of these compounds chlortetracycline was introduced in 1948. Soon after their development tetracyclines were found to be highly effective against various pathogens including rickettsiae, Gram-positive, and Gram-negative bacteria, thus, becoming a class of broad-spectrum antibiotics. The mechanism of action of tetracyclines is thought to be related to the inhibition of protein synthesis by binding to the 30S bacterial ribosome. Tetracyclines are also an effective anti-malarial drug. Over time, many other "protective" actions have been described for tetracyclines. Minocycline, which can readily cross cell membranes, is known to be a potent anti-apoptotic agent. Its mechanism of action appears to relate to specific effects exerted on apoptosis signaling pathways. Another tetracycline, doxycycline is known to exert antiprotease activities. Doxycycline can inhibit matrix metalloproteinases, which contribute to tissue destruction activities in diseases such as gingivitis. A large body of literature has provided additional evidence for the "beneficial" actions of tetracyclines, including their ability to act as oxygen radical scavengers and anti-inflammatory agents. This increasing volume of published work and ongoing clinical trials supports the notion that a more systematic examination of their possible therapeutic uses is warranted. This review provides a summary of tetracycline's multiple mechanisms of action and while using the effects on the heart as an example, this review also notes their potential to benefit patients suffering from various pathologies such as cancer, Rosacea, and Parkinson's disease.

In growing pigs, chlortetracycline induces a reversible green bone discoloration and a persistent increase of bone mineral density dependent of dosing regimen

We studied in growing pigs the effects of exposure to dietary chlortetracycline on bone mineral density (BMD) and bone color. Pigs were randomly allocated to a drug-free diet (n=48) or a diet fortified with 800 ppm of chlortetracycline, starting either at 28- or 84-d of age, and for either a 28- or 56-d duration (n=16 pigs/group). The lumbar vertebral discoloration and BMD of randomly chosen pigs were evaluated at 28-d intervals up to 168-d of age. The odds of bone discoloration increased with dosing duration and age at treatment onset, and decreased with the withdrawal time and age at treatment onset interaction (p < or = 0.001). The measured trabecular BMD linearly increased with age and squared treatment duration (p < or = 0.005). Therefore, TC-induced bone discoloration is reversible, and may be prevented with proper dosing regimen design. Moreover, TC induces a persistent increase on BMD that could be detected with quantitative computed tomography.

Effect of an antimicrobial agent on atherosclerotic plaques: assessment of metalloproteinase activity by molecular imaging

OBJECTIVES

Technetium-99m-labeled matrix metalloproteinase inhibitor (MPI) was used for the noninvasive assessment of matrix metalloproteinase (MMP) activity in atherosclerotic plaques after minocycline (MC) intervention.

BACKGROUND

MMP activity in atherosclerosis contributes to plaque instability. Some antimicrobial agents may attenuate MMP activity.

METHODS

Atherosclerotic lesions were produced in 38 rabbits with a high cholesterol diet for 4 months; 5 groups of rabbits, in the fourth month, received fluvastatin (FS) (n = 6), low-dose MC (n = 7), high-dose MC (n = 7), a combination of low-dose MC and FS (n = 6), or no intervention (n = 12); 8 unmanipulated rabbits were used as disease controls. Micro-single-photon emission computed tomography imaging was performed in all animals after intravenous MPI administration, followed by pathologic characterization of the aorta. A cell culture study evaluated the effect of MC on MMP production by activated human monocytes.

RESULTS

MPI uptake was visualized best in untreated atherosclerotic animals (percent injected dose per gram MPI uptake, 0.11 +/- 0.04%). MPI uptake was reduced in the FS (0.06 +/- 0.01%; p < 0.0001), high-dose MC (0.05 +/- 0.01%; p < 0.0001), and MC-FS (0.05 +/- 0.005%; p < 0.0001) groups. Low-dose MC did not resolve MPI uptake significantly (0.08 +/- 0.02; p = 0.167). There was no incremental benefit of the combination of MC and FS. MPI uptake showed a significant correlation with plaque MMP-2, and MMP-9 activity. MMP-9 release from tumor necrosis factor-alpha-activated macrophages was abrogated by incubation with MC.

CONCLUSIONS

Molecular imaging of MMP activity in atherosclerotic plaque allows for the study of the efficacy of therapeutic interventions. MC administration resulted in substantial reduction in plaque MMP activity and histologically verified plaque stabilization. MC was found to be equally effective as FS.

Tetracyclines inhibit rat osteoclast formation and activity in vitro and affect bone turnover in young rats in vivo

An experiment was designed to investigate whether systemic administration of tetracyclines (TCs) as bone fluorochrome labels could interfere with bone modeling in vivo and inhibit osteoclast formation and activity in vitro. Cell cultures of rat bone marrow macrophages revealed that TC and oxytetracycline inhibited osteoclastogenesis and bone resorption and stimulated apoptosis. Forty rats in five groups were treated with saline, calcein green, alizarin red S, TC, or oxytetracycline. Their tibias were used for histomorphometric analysis, including bone static, dynamic, and resorption parameters in the tibial proximal metaphysis. No significant differences in bone volume per tissue volume, trabecular number, trabecular thickness, trabecular separation, bone formation rate per bone surface, mineralizing surface, or mineral apposition rate were observed. TC or oxytetracycline decreased eroded surface, number of osteoclasts per bone perimeter, and osteoclast surface per bone surface by about 50%. The results demonstrated that TC and oxytetracycline inhibit rat osteoclast formation and activity in vitro, and histomorphometric parameters involved in bone turnover may be affected by the use of oxytetracycline and TC as fluorescent bone labels in vivo.

Sustained and localized in vitro release of BMP-2/7, RANKL, and tetracycline from FlexBone, an elastomeric osteoconductive bone substitute

We tested the hypothesis that synthetic composites containing a high percentage of osteoconductive biominerals well-integrated with a hydrophilic polymer matrix can be engineered to provide both the structural and biochemical framework of a viable synthetic bone substitute. FlexBone, an elastic hydrogel-mineral composite exhibiting excellent structural integration was prepared by crosslinking poly(2-hydroxyethyl methacrylate) hydrogel in the presence of 25 wt% nanocrystalline hydroxyapatite and 25 wt% tricalcium phosphate. Biologically active factors tetracycline, BMP-2/7, and RANKL that stimulate bone formation and remodeling were encapsulated into FlexBone during polymerization or via postpolymerization adsorption. SEM and dynamic mechanical analyses showed that the encapsulation of tetracycline (5.0 wt%) did not compromise the structural integrity and compressive behavior of FlexBone, which could withstand repetitive megapascal-compressive loadings and be securely press-fitted into critical femoral defects. Dose-dependent, sustained in vitro release of tetracycline was characterized by spectroscopy and bacterial inhibition. A single dose of 40 ng BMP-2/7 or 10 ng RANKL pre-encapsulated with 50 mg FlexBone, released over 1 week, was able to induce local osteogenic differentiation of myoblast C2C12 cells and osteoclastogenesis of macrophage RAW264.7 cells, respectively. With a bonelike structural composition, useful surgical handling characteristics, and tunable biochemical microenvironment, FlexBone provides an exciting opportunity for the treatment of hard-to-heal skeletal defects with minimal systemic side effects.

Tetracyclines and chemically modified tetracycline-3 (CMT-3) modulate cytokine secretion by lipopolysaccharide-stimulated whole blood

In addition to their bacteriostatic effect, tetracyclines, which are often used in the treatment of periodontitis, also present anti-inflammatory properties. In the present study, we investigated the effects of tetracycline (TC), doxycycline (doxy), and chemically modified tetracycline-3 (CMT-3) on the production of pro-inflammatory mediators and matrix metalloproteinases (MMPs) in an ex vivo human whole blood (WB) model stimulated with Porphyromonas gingivalis lipopolysaccharide (LPS). WB samples obtained from three periodontitis patients and six healthy subjects were stimulated with P. gingivalis LPS in the absence and presence of TC, doxy, or CMT-3. The secretion of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8), MMP-8, and MMP-9 by the WB samples was determined using enzyme-linked immunosorbent assays. P. gingivalis LPS significantly increased the secretion of all cytokines and MMPs tested. While we observed inter-patient variations, TC, doxy, and CMT-3 caused reductions of LPS-induced cytokine secretion to various degrees. TC, doxy, and CMT-3 had no significant effect on MMP-8 and MMP-9 secretion by LPS-stimulated WB samples. In conclusion, we used a human WB model that takes into consideration relevant in vivo immune cell interactions in the presence of plasma proteins to show that TC, doxy, and CMT-3 can reduce the production of pro-inflammatory mediators. This property may contribute to the clinically proven benefits of these molecules in the treatment of periodontitis and other chronic inflammatory diseases.

Effect of systemic tetracycline on the degradation of tetracycline-impregnated bilayered collagen membranes: an animal study

BACKGROUND

Premature collagen membrane degradation may compromise the outcome of osseous regenerative procedures. Tetracyclines (TTCs) inhibit the catalytic activities of human metalloproteinases. Preprocedural immersion of collagen membranes in TTC and systemic administration of TTC may be possible alternatives to reduce the biodegradation of native collagen membranes.

AIM

To evaluate the in vivo degradation of collagen membranes treated by combined TTC immersion and systemic administration.

MATERIALS AND METHODS

Seventy-eight bilayered porcine collagen membrane disks were divided into three groups and were immersed in 0, 50, or 100 mg/mL TTC solution. Three disks, one of each of the three groups, were implanted on the calvaria of each of 26 Wistar rats. Thirteen (study group) were administered with systemic TTC (10 mg/kg), while the remaining 13 received saline injections (control group). Calvarial tissues were retrieved after 3 weeks, and histological sections were analyzed by image analysis software.

RESULTS

Percentage of remaining collagen area within nonimpregnated membranes was 52.26 ± 20.67% in the study group, and 32.74 ± 13.81% in the control group. Immersion of membranes in 100 mg/mL TTC increased the amount of residual collagen to 63.46 ± 18.19% and 42.82 ± 12.99% (study and control groups, respectively). Immersion in 50 mg/mL TTC yielded maximal residual collagen values: 80.75 ± 14.86% and 59.15 ± 8.01% (study and control groups, respectively). Differences between the TTC concentrations, and between the control and the study groups were statistically significant.

CONCLUSIONS

Immersion of collagen membranes in TTC solution prior to their implantation and systemic administration of TTC significantly decreased the membranes' degradation.

Inhibitors of Clostridium histolyticum colagenase

Different substances were tested as inhibitors of Clostridium histolyticum collagenase, both experimental and theoretically. The in vitro collagenase activity, alone and in the presence of inhibitors, was quantified by reaction with bovine collagen and dosage of the releasing amino acids. Collagenase-inhibitor interaction was studied theoretically by docking computational calculations. Only one among the tested substances showed inhibitor activity against the bacterial collagenase.

Biodegradation of three different collagen membranes in the rat calvarium: a comparative study

BACKGROUND

Collagen barrier membranes are commonly applied in periodontal and bone-regenerative procedures. Membranes differ in their resorption pattern following implantation, thus influencing clinical outcome. The purpose of this study was to quantitatively evaluate the biodegradation of three different commercially available collagen membranes.

METHODS

Collagen membranes were cut into 5-mm-diameter disks and labeled with aminohexanoyl-biotin-N-hydroxy-succinimide ester. One membrane disk of each type (non-cross-linked [NCL], glutaraldehyde cross-linked [GCL], and ribose cross-linked [RCL]) was implanted on the calvaria of 20 Wistar rats. Block sections were retrieved after 2 days (baseline, two animals), 14 days (10 animals), or 28 days (eight animals). Decalcified histologic sections were stained with streptavidin horseradish peroxidase. Residual membrane thickness and area were measured. Statistical analysis consisted of analysis of variance (ANOVA) with repeated measures.

RESULTS

Statistically significant differences in the amount of residual membrane material were recorded within each membrane (among different time points) and among different membranes at the same time points (P <0.001). At 28 days, the least amount of residual collagen area, expressed as the percentage of baseline, was observed in the NCL group (13.9% +/- 10.25%), followed by the GCL (24.7% +/- 35.11%) and RCL (91.3% +/- 10.35%) groups. Residual membrane thickness, expressed as the percentage of baseline thickness, presented a similar pattern (31% +/- 16.55%, 37% +/- 41.90%, and 94.1% +/- 12.22%, respectively). ANOVA with repeated measures showed a significant interaction between membranes and time (P <0.001).

CONCLUSIONS

The tested membranes differed in their degradation patterns and collagen contents. Membranes should be chosen for each clinical case according to the desired biodegradation characteristics.

Urinary matrix metalloproteinase -8, -9, -14 and their regulators (TRY-1, TRY-2, TATI) in patients with diabetic nephropathy

Matrix metalloproteinase-9 (MMP-9) has been shown to be involved in the development of diabetic nephropathy (DNP). We studied the levels, molecular forms, and degree of activation of urinary MMP-8, -9, -14, trypsin-1 and -2, as well as tumor-associated trypsin inhibitor (TATI) of DNP patients and healthy controls. Urinary samples were analyzed for MMPs by Western blotting and gelatin zymography and for trypsin-1, -2, and TATI by time-resolved immunofluorometric assays. Total MMP-8 immunoreactivity, the proportion of active MMP-9, and gelatinolytic activity in urine were significantly higher in DNP patients than in controls. In urine of DNP patients the proportion of active polymorphonuclear neutrophil (PMN)-type (but not fibroblast-type) MMP-8 was increased. MMP-8 and MMP-9 were found to form high molecular weight complexes in DNP urine. Total immunoreactivity of soluble urinary MMP-14 and the levels of trypsin (TRY)-1 and TRY-2, but not of TATI, were also significantly increased in DNP. Zymography, Western blotting, and immunofluorometric analysis of DNP urine showed a significant association especially between activation of MMP-9 as well as PMN-type MMP-8 and TRY-2. Our findings suggest that a trypsin-MMP cascade is involved in the pathogenesis of DNP, which may offer new possibilities for diagnosis and treatment of DNP with MMP inhibitors.

Induction of inflammatory cytokines by a keratin mutation and their repression by a small molecule in a mouse model for EBS

Epidermolysis bullosa simplex (EBS) is a skin disorder caused by mutations in keratin (K) 5 or K14 genes. It is widely regarded as a mechanobullous disease, resulting from a weakened cytoskeleton, causing extensive cytolysis. It was postulated by others that certain K14 mutations induce tumor necrosis factor-alpha (TNF-alpha) and increase apoptosis. Here, we report that in K5-/- mice and in a cell culture model of EBS, the mRNA and protein levels of TNF-alpha remain unaltered. Transcriptome analysis of K5-/- mice revealed, however, that the proinflammatory cytokines IL-6 and IL-1beta were significantly upregulated at the mRNA level in K5-/- mouse skin. These results were confirmed by TaqMan real-time PCR and ELISA assays. We hypothesize that keratin mutations contribute to EBS in a mouse model by inducing local inflammation that mediates a stress response. Following clinical reports, we applied the small molecule doxycycline to K5-/- mice. We demonstrate that doxycycline extended the survival of neonatal K5-/- mice from less than 1 to up to 8 hours. Microarray and TaqMan real-time PCR showed a downregulation of matrix metalloproteinase 13 and IL-1beta, indicating an effect of doxycycline on transcription. Our data offer a novel small molecule-based therapy approach for EBS.

CMT-3 inhibits orthodontic tooth displacement in the rat

OBJECTIVE

Orthodontic tooth movement requires extensive remodeling of the periodontal ligament (PDL) and the alveolar bone. Osteoclasts resorb bone, allowing teeth to migrate in the direction of the force. Matrix metalloproteinases (MMPs) are able to degrade the extracellular matrix of the periodontal tissues. Chemically modified tetracyclines (CMTs) can inhibit MMPs, but lack antimicrobial activity. We hypothesize that CMT-3 will decrease the rate of orthodontic tooth movement in the rat.

DESIGN

Eighteen Wistar rats received a standardized orthodontic appliance at one side of the maxilla. During 14 days, three groups of six rats received a daily dose of 0, 6 or 30mg/kg CMT-3, and tooth displacement was measured. Thereafter, osteoclasts were counted on histological sections using an ED-1 staining. Multi- and mononuclear ED-1-positive cells in the PDL were also counted. In addition, sections were stained for MMP-9.

RESULTS

CMT-3 significantly inhibited tooth movement (p=0.03) and also decreased the number of osteoclasts at the compression sides in the 30mg/kg group (p<0.05). Significantly more mono- than multinuclear ED-1-positive cells were present in the PDL, but no significant differences were found between the dosage groups. Osteoclasts in the 30mg/kg group seemed to contain less MMP-9 than in the control.

CONCLUSIONS

CMT-3 inhibits tooth movement in the rat, probably by reducing the number of osteoclasts at the compression side. This might be due to induction of apoptosis in activated osteoclasts or reduced osteoclast migration. Reduced MMP activity by CMT-3 might also directly inhibit degradation of the organic bone matrix.

Role of matrix metalloproteinase inhibitors in preventing abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a significant health problem in the United States, with approximately 30,000 repair operations annually. Treatment of AAA is associated with more than 150,000 hospital admissions per year. The development of AAA is characterized by destruction of the elastic media of the aortic wall. A large body of evidence suggests that a group of enzymes called matrix metalloproteinases (MMPs) plays a significant role in the destruction of extracellular matrix in the aortic wall. MMP inhibition has, therefore, been viewed as an alternative pharmacotherapeutic approach to slow down the development and progression of small AAAs, thus reducing the need for surgical intervention.

The role of mesenchymal cells in the pathophysiology of inflammatory arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder of the joints that can cause severe disability. While the role of inflammatory cells in the pathogenesis of RA has been well established, the specific contribution of resident cells within the synovial membrane, especially those of mesenchymal origin, has become the object of closer scrutiny only recently. The central position of these cells in the disease process of RA is underlined by their involvement in its main pathophysiological features: inflammation, hyperplasia and joint destruction. In this chapter, we provide a characterisation of resident mesenchymal cells, specifically fibroblast-like cells in the rheumatoid synovium, and give an overview of the molecular pathways by which these cells are involved in the initiation and perpetuation of RA.

Gingival crevicular fluid matrix metalloproteinase-13 levels and molecular forms in various types of periodontal diseases

BACKGROUND

The purpose of this study was to evaluate the levels, molecular forms and activation degree of matrix metalloproteinase-13 (MMP-13) in the gingival crevicular fluid (GCF) of patients with periodontal diseases and to correlate these findings with periodontal clinical parameters.

METHODS

Sixty one subjects participated in this study as healthy (n = 18), gingivitis (n = 17), aggressive periodontitis (AgP; n = 15) and chronic periodontitis (CP; n = 11) groups. Clinical measurements and GCF samples were obtained from each subject. The molecular forms of MMP-13 in GCF samples were analyzed by Western immunoblotting method. Differences among the groups were assessed using non-parametric statistical analysis.

RESULTS

In the CP group, levels of 29-30 kDa fragment of MMP-13, total MMP-13, and activated form of MMP-13 were significantly higher than in the healthy, gingivitis and AgP groups. GCF levels of all molecular forms of MMP-13 in AgP group were similar to those of healthy and gingivitis groups. Total and activated MMP-13 levels were positively correlated with all clinical parameters. 29-30 kDa fragment levels of MMP-13 were also positively correlated with papillary bleeding index and plaque index.

CONCLUSION

These results indicate that elevated GCF MMP-13 levels may play an important role in the pathogenesis of CP. These data demonstrate, for the first time, pathologically activated and elevated MMP-13 in GCF.

Chemically modified tetracyclines stimulate matrix metalloproteinase-2 production by periodontal ligament cells

BACKGROUND AND OBJECTIVE

The purpose of this study was to investigate the effects of chemically modified tetracyclines (CMTs) on the production of gelatinases [matrix metalloproteinase (MMP)-2 and -9] by human periodontal ligament (PDL) cells, and on the activity of recombinant gelatinases.

MATERIAL AND METHODS

Human PDL cells were cultured with CMT-1, -3, -5, -7 or -8 in concentrations of 0, 1, 5, 10, 20, 50, 100, 200 and 500 microm. Gelatin zymography was used to determine MMP-2 and -9 production of the cells. The amount of DNA present in the cultures was analyzed using a fluorescent assay. The cytotoxicity of the CMTs was also determined. Recombinant human MMP-2 and -9 were incubated with the CMTs (0-500 microm) and their activity was analyzed using an internally quenched fluorogenic substrate.

RESULTS

MMP-2 production was stimulated up to sevenfold by CMT-1, -3, -7 and -8 at low concentrations (10-200 microm). No significant amounts of MMP-9 were produced. In contrast, MMP-2 and -9 activity was reduced by approximately 10-40-fold at higher concentrations (200-500 microm). CMT-5 had no effect on the production or on the activity of MMP-2 and -9. Only CMT-3 and -8 had cytotoxic effects on the PDL cells at the highest concentrations.

CONCLUSION

Surprisingly, CMTs are able to stimulate MMP-2 production at relatively low concentrations. However, at higher concentrations they exert a much stronger inhibitory effect on gelatinase activity. A possible stimulatory effect of CMTs on MMP production should be considered in their clinical use.

Chemically modified tetracyclines (CMT-3 and CMT-8) enable control of the pathologic remodellation of human aortic valve stenosis via MMP-9 and VEGF inhibition

OBJECTIVE

Tetracycline derivatives affect many cellular functions relevant to chronic cardiovascular pathologies, including cell proliferation, migration and matrix remodelling. Accordingly, we sought to determine whether they may modulate the pathologic characteristics known to be significantly involved in human aortic valve stenosis, such as gelatinase production, apoptosis, expression of vascular endothelial growth factor (VEGF) and tumour necrosis factor-alpha (TNF-alpha).

METHODS

The effects of tetracycline derivatives (tetracycline and CMTs-3, -5, -8) on MMP-2 and -9 and their endogenous tissue inhibitor (TIMP-1 and -2) production profiles in explanted human aortic valve pieces were examined by means of gelatine zymography and reverse zymography. Chemiluminescent ELISA was performed to assess VEGF and TNF-alpha concentrations in the medium, and in order to evaluate programmed cell death, in situ labelling of the 3'-ends of the DNA fragments generated by apoptosis-associated endonucleases was performed.

RESULTS

CMT-3 and -8 lowered the MMP-9 and VEGF levels significantly in a drug-, dose-, and time-dependent manner. MMP-2 and TIMPs remained unchanged, emphasizing the specificity of CMTs to MMP-9 production on the one hand and restoring the beneficial equilibrium of MMP-9 and TIMPs on the other. Tetracycline was the only drug with a significant impact on net gelatinolytic activity, suggesting that the effect of tetracycline is more extensive concerning total MMP activity.

CONCLUSIONS

Tetracycline derivatives may have therapeutic effects on the pathologic remodellation of advanced human aortic stenosis through the inhibition of MMP-9 and VEGF production.

Role of matrix metalloproteinases in HaCaT keratinocytes apoptosis induced by loxosceles venom sphingomyelinase D

Envenomation by the spider Loxosceles (brown spider) can result in dermonecrosis and severe ulceration. We have previously shown that Loxosceles sphingomyelinase D (SMaseD), the enzyme responsible for these pathological effects, induced expression of matrix metalloproteinase-9 (MMP-9), which is possibly one of the main factors involved in the pathogenesis of the cutaneous loxoscelism. The aim of this study was to further investigate the molecular mechanisms triggered by Loxosceles SMaseD involved in the initiation of the dermonecrotic lesion, using HaCaT cultures, a human keratinocyte cell line, as an in vitro model for cutaneous loxoscelism. We show here that SMaseD from Loxosceles spider venom induces apoptosis in human keratinocytes, which is associated with an increased expression of metalloproteinase-2 and -9, and that the use of metalloproteinase inhibitors, such as tetracycline, may prevent cell death and potentially may prevent tissue destruction after envenomation.

Dynamics of Subcutaneous Tissue Response to the Implantation of Tetracycline-Treated or Untreated Membrane of Demineralized Bovine Cortical Bone in Rats

This study aims to conduct a histological evaluation of tissue response to a membrane obtained from demineralized bovine cortical bone, associated or not, to tetracycline (TTC). TTC treated and untreated bovine membranes were implanted in the subcutaneous tissue of rats ( n = 120). The animals were killed 1, 3, 7, 15, 30, and 60 days after surgery. The tissue around the material was fixed in 10% buffered formalin for 24 h. Sections of 6 mm were stained with hematoxylin and eosin. In general, moderate to intense inflammatory response was observed in the initial periods (1 and 3 days), moderate response in the 7- and 15-day periods, and that was remarkably reduced at 30 and 60 days. Resorptions of the membranes by mononuclear cells (fibroblasts and macrophages) and multinucleated giant cells were observed 15 days after implantation. Only the remnants of the material could be detected in some animals in 60 days. Both membranes were tolerated by the tissue and were completely resorbed after 30-60 days. While the association of TTC apparently accelerated the biodegradability of the membrane substrate, no significant differences were found in the tissue response behavior between the two groups tested.

Matrix metalloproteinase-2 (MMP-2) and MMP-9 in pulmonary pathology

The lung is affected by a variety of disease processes that can lead to considerable morbidity and mortality. As the lung is the only organ for respiration and gas exchange, the structural and functional integrity of the lung is of primary importance. Various pathological processes affect the extracellular matrix (ECM) of the lung in an adverse manner, causing destruction of tissue integrity followed by tissue remodeling, which together impair normal pulmonary function. Matrix metalloproteinases (MMPs) are neutral proteinases that are involved in the breakdown and remodeling of the ECM under a variety of physiological and pathological conditions. MMP-2 and MMP-9, collectively known as the gelatinases, are particularly important in the pathogenesis of inflammatory, infectious, and neoplastic diseases in many organs including the lung. This review examines the expression of MMP-2 and MMP-9 in disease of the lung and discusses the role these gelatinases may play in disease progression.

Effect of chemically modified tetracycline on transforming growth factor-beta1 and caspase-3 activation in liver of septic rats

OBJECTIVES

We have previously demonstrated that hepatic matrixmetalloproteinase (MMP)-9 and gelatinase activity increased significantly after sepsis, and pretreatment with chemically modified tetracycline (CMT-3) inhibited these expressions and improved survivability. It has been established that MMP-9 release from hepatic nonparenchymal cells activates transforming growth factor (TGF)-beta1, which in turn catalyzes the conversion of procaspase-8 into active caspase-8. Caspase-8 activates caspase-3, which in turn degrades fibronectin and focal adhesion kinase and leads to disruption of hepatic architecture and integrity. We have been interested in investigating the role of posttreatment with CMT-3 on hepatic MMP-9, TGF-beta1, and caspase-3 activity following sepsis.

DESIGN

Laboratory experiment.

SETTING

University laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

In this study, sepsis was induced in rats by cecal ligation and puncture (CLP), and 2 hrs later, half of the rats received CMT-3 (25 mg/kg), whereas the other half received vehicle by gavage. Twenty-four and 48 hrs after sepsis induction, blood and liver samples were collected.

MEASUREMENTS AND MAIN RESULTS

Plasma glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) levels were determined by enzymatic method, and the activation states of hepatic MMP-9, MMP-2, tissue inhibitor of metalloproteinase (TIMP)-1, TGF-beta1, and caspase-3 were determined by Western immunoblotting. Plasma GOT, GPT, and hepatic MMP-9 activity increased 2.5-fold, and TFG-beta1 and caspase-3 activity increased 1.5- to 2-fold at 24 hrs and 48 hrs post-CLP; CMT-3 treatment blocked these increases. Furthermore, CMT-3 treatment also led to increased TIMP-1 level, an in vivo inhibitor of MMP-9. MMP-2 level was unaffected by CLP. The 24-hr and 48-hr mortality rates for CLP rats were 29% and 50%, whereas posttreatment with CMT-3 resulted in 0% mortality.

CONCLUSIONS

Our results are consistent with an MMP-9-induced caspase-3 activation in response to CLP. CMT-3 posttreatment increased TIMP-1 level and thereby inhibited MMP-9, which in turn decreased TGF-beta1 and caspase-3 signaling pathways and improved survivability in septic rats.

1,12-Substituted tetracyclines as antioxidant agents

Novel hydroxypyrazoline derivatives of tetracycline and minocycline have been synthesized through the reaction of these tetracyclines with hydrazine. The formation of a new chiral center at C12 is stereospecific to give 12S-12-hydroxy-1,12-pyrazolinotetracycline. A reaction mechanism for the formation of these novel tetracycline derivatives has been proposed. Hydroxypyrazolinotetracyclines exhibit no binding to Mg2+ and Zn2+, features that are required for antibiotic activity and matrix metalloproteinase (MMP) inhibitions, respectively. The modification toward their hydroxypyrazolino derivatives significantly improved the antioxidant activities of tetracycline and minocycline, as shown by three commonly used assays (DPPH, ABTS+, and superoxide scavenging). 12S-Hydroxy-1,12-pyrazolinominocycline is a promising tetracycline-based antioxidant devoid of antibiotic properties and MMP inhibitory activity, which could be beneficial in the treatment of complications related to oxidative stress.

Modulating the Effects of Diabetes on Osseointegration With Aminoguanidine and Doxycycline

BACKGROUND

The current knowledge of wound healing around implant surfaces is quite limited, particularly as it relates to the effects of systemic diseases such as diabetes. The purpose of our research is to histologically evaluate the effects of aminoguanidine and doxycycline in the modification of peri-implant wound healing around endosseous implants in diabetic rats.

METHODS

Thirty-two Sprague-Dawley rats were randomly assigned to four different treatment groups. One group served as the non-diabetic control, while diabetes was induced in other groups. Titanium plasma-sprayed (TPS) implants were placed in the femora of each animal 2 weeks following diabetic induction. One group of diabetic rats was given aminoguanidine via intraperitoneal injection, and another given doxycycline via oral gavage for 28 days beginning on the day of implantation. The third group of diabetic rats received no medication (controls). All animals were sacrificed following 28 days of healing.

RESULTS

The results were measured by marrow bone-to implant contact (MBIC) between the groups. Values for MBIC were greater for the non-diabetic control group than the diabetic control group (P < 0.001). Aminoguanidine-treated diabetic animals had a significantly greater MBIC than the diabetic control group (P < 0.01). Diabetic animals receiving doxycycline did not differ significantly from the diabetic control group (P > 0.05).

CONCLUSIONS

The results of this study using a rat model con- firm previous reports that diabetes inhibits osseointegration, as defined by MBIC. In addition, this study demonstrates that the detrimental effects of diabetes on osseointegration can be modified using aminoguanidine systemically. However, systemic administration of doxycycline only slightly enhances osseointegration.

Effects of doxycycline on mechanical properties of bones in rats with ovariectomy-induced osteopenia

Tetracyclines have been reported to inhibit bone resorption and intensify bone formation. The aim of the present study was to investigate the effects of doxycycline (20 mg/kg PO daily for 28 days) on bone mechanical properties in bilaterally ovariectomized and sham-operated rats. The experiment was carried out on 3-month-old Wistar rats. Mechanical properties of the whole femur (extrinsic stiffness, ultimate and breaking load, deformation caused by applied load) and the femoral neck (load at fracture) as well as bone mass and bone mineral content in the tibia, femur, and L4 vertebra were examined. Bilateral ovariectomy resulted in decreases in bone mineral content/bone mass ratio and worsening of mechanical properties of the femoral neck. The changes were counteracted by doxycycline. Doxycycline reversed the effect of ovariectomy on load at fracture of the femoral neck. Doxycycline did not significantly affect the mechanical properties of bones in the sham-operated rats.

Tetracycline Impregnation Delays Collagen Membrane Degradation In Vivo

BACKGROUND

Guided tissue and bone regeneration using bioabsorbable collagen membranes is a common practice. Collagen promotes progenitor cell adhesion, chemotaxis, homeostasis, and physiologic degradation with low immunogenicity, which makes it an ideal material for barrier preparation. Collagen membranes have to maintain integrity for a proper time, thus ensuring successful cell exclusion. Early collagen membrane degradation is detrimental for the success of regenerative procedures. This in vivo study was conducted to evaluate the effect of soaking collagen membranes in different tetracycline hydrochloride (TCN) concentration solutions on its degradation.

METHODS

Five mm disks of collagen membrane were soaked in either 100 mg/ml TCN (group 100) or 50 mg/ml TCN (group 50); a group of non-treated disks served as controls. All disks were labeled with aminohexanoyl-biotin-N-hydroxy-succinimide ester (biotin) and implanted in rat calvaria bone. Block sections were taken after 3 weeks and histological slides stained with horseradish peroxidase (HRP) to detect remnants of biotinylated collagen. Staining intensity was analyzed by image-analysis software taking quadruplicate measurements of a 500 microm2 area each. Data were analyzed using analysis of variance (ANOVA) with repeated measures and paired t test with Bonferroni correction.

RESULTS

Staining intensity of membranes in group 100 was > 5-fold higher than the control while group 50 exhibited > 11-fold higher intensity than the control and > 2.5-fold higher than the 100. All of these differences were statistically significant (P < 0.001).

CONCLUSION

Soaking collagen membranes in 50 mg/ml TCN solution is a useful, practical, and simple tool to slow membrane degradation.

Chemically modified tetracyclines act through multiple mechanisms directly on osteoclast precursors

Chemically modified tetracyclines (CMTs) are thought to inhibit bone resorption primarily through their ability to inhibit matrix metalloproteinases (MMPs). We have previously demonstrated that some tetracycline compounds (TCs) induce apoptosis in mature rabbit osteoclasts and inhibit osteoclastic resorption in mouse osteoblast/marrow co-cultures in vitro. In this report, we now show that non-antibiotic analogues of doxycycline (CMT-3) and minocycline (CMT-8) are potent inhibitors of osteoclastogenesis in vitro from human peripheral blood mononuclear cells (PBMC) stimulated with macrophage colony stimulating factor (MCSF) and receptor activator of NF-kappaB ligand (RANKL), through an action that is independent of osteoblast-osteoclast interactions. Osteoclast formation over 20 days was completely abrogated when CMT-3 or CMT-8 were included in PBMC cultures at a concentration of 250 ng/ml, although doxycycline at this concentration reduced osteoclast formation to ca. 50% of control. CMT-3 and CMT-8 also significantly induced apoptosis over 24 h in mature osteoclasts generated over 20 days when added to cultures at 5 microg/ml or more. In a time-course experiment, apoptosis was evident after a delay of 1-2 h following treatment of mature osteoclasts with CMT-3 at 20 microg/ml. The broad-spectrum MMP inhibitor BB94 (Batimastat) did not recapitulate the apoptosis induced by CMT-3, even at a concentration where MMP-13 activity was completely inhibited. There was no evidence for an anabolic effect of any of the TCs on osteoblast lineage cells in a calcifying fibroblastic colony (CFU-f) formation assay, where CMT-3 partially inhibited CFU-f formation at 5 microg/ml. Our data indicate that inhibition of osteoclast formation and induction of osteoclast apoptosis are pharmacologically significant actions of CMTs in inhibiting bone resorption, and that osteoclast apoptosis cannot be attributed to the ability of CMTs to inhibit MMPs or to actions mediated by osteoblastic lineage cells.

Chemically modified tetracyclines selectively inhibit IL-6 expression in osteoblasts by decreasing mRNA stability

In bone biology, interleukin (IL)-6 is an autocrine/paracrine cytokine which can induce osteoclasts formation and activation to help mediate inflammatory bone destruction. Previous studies have shown that tetracycline and its derivatives have potentially beneficial therapeutic effects in the prevention and treatment of metabolic bone diseases by modulating osteoblast and osteoclast activities. Our previous studies indicated that non-antimicrobial chemically modified tetracyclines (CMTs) can dose-dependently inhibit IL-1 beta-induced IL-6 secretion in osteoblastic cells. In the present study, we explored the molecular mechanisms underlying the ability of doxycycline analogs CMT-8 and its non-chelating pyrazole derivative, CMT-5 to affect IL-6 gene expression in murine osteoblasts. Steady-state IL-6 mRNA was decreased with CMT-8 (ca. 50%) but not by CMT-5 when stimulated by IL-1 beta. CMT-8 regulation of IL-1 beta-induced IL-6 gene expression was further explored. CMT-8 did not affect IL-6 promoter activity in reporter gene assays. However, the IL-6 mRNA stability was decreased in the presence of CMT-8. These effects require de novo protein synthesis as they were inhibited by cycloheximide. Western blot analysis indicated that CMT-8 did not affect p38 mitogen-activated protein kinase, c-jun NH(2)-terminal kinases, or extracellular signal-regulated kinases (1 and 2) phosphorylation in response to IL-1 beta. These data suggest that CMT-8 can modulate inhibit IL-1 beta-induced IL-6 expression in MC3T3-E1 cells at the post-transcriptional level affecting IL-6 mRNA stability. These observations may offer a novel molecular basis for this treatment of metabolic bone diseases that are mediated by IL-6.

Levels and molecular forms of MMP-7 (matrilysin-1) and MMP-8 (collagenase-2) in diseased human peri-implant sulcular fluid

OBJECTIVES

Matrix metalloproteinases (MMPs) play crucial role in various tissue destructive inflammatory processes by degrading almost all peri-cellular and basement membrane components. MMP-8 (collagenase-2) is the major MMP in periodontitis. MMP-7 (matrilysin-1), in addition to its ability to degrade matrix and basement membrane components, activates other latent pro-MMPs and defensins, host cell-derived antimicrobial cryptidins. The aim of the present study was to characterize the relationship, levels and molecular forms of MMP-8 and MMP-7 in diseased peri-implant sulcular fluid (PISF).

MATERIALS AND METHODS

Seventy-two human dental implant fluid samples were collected with filter paper strips from peri-implant sulci from healthy and untreated diseased implant sites. Gingival index (GI) and/or bone resorption (BR) were also recorded. Western immunoblot method with polyclonal anti-human-MMP-8 and monoclonal anti-human-MMP-7 antibodies was used, and immunoreactivities were quantified with computer scanning program. The effects of MMP inhibitors (doxycycline, chemically modified tetracycline-3, clodronate, CTT-peptide and marimastat) were studied on the activity of recombinant human matrilysin-1 (MMP-7) using beta-casein degradation assay.

RESULTS

The levels of active forms of MMP-8 and MMP-7 were significantly elevated in diseased PISF in relation to healthy PISF. Furthermore, MMP-8 and MMP-7 levels correlated significantly to each other and GI. MMP-8 was present not only as bands corresponding to 75-kDa polymorphonuclear leukocyte (PMN) -type pro- and 65-kDa active forms, but also as 55-kDa non-PMN-type pro- and 45-kDa active forms. Immunoreactivities > 80 kDa most likely represented dimeric and/or inhibitor-bound MMP-8 complexes and the low molecular weight (< 30 kDa) species were apparently degraded fragments. In diseased PISF, 19-21-kDa active MMP-7 and 28-30-kDa pro-MMP-7 species were detected, and the active 19-21-kDa forms of MMP-7 predominated in diseased PISF. Doxycycline (50 micro m and 250 micro m), chemically modified non-antimicrobial tetracycline (CMT-3) (50 micro m and 100 micro m), clodronate (a bisphosphonate, 20 micro m and 500 micro m) and the cyclic CTT (CTTHWGFTLC)-peptide (125 micro m and 250 micro m), all known broad-spectrum or selective MMP-inhibitors, did not inhibit the activity of human recombinant MMP-7; only marimastat (1 micro m and 5 micro m) inhibited MMP-7.

DISCUSSION

Increased immunoreactivities of the active MMP-8 and MMP-7 species in PISF from diseased peri-implantitis lesions eventually reflect the stage and course of peri-implantitis; MMP-7 may potentially act as MMP-8 and defensin activator in diseased PISF.

CONCLUSION

The elevated levels of MMP-8 and matrilysin-1/MMP-7 were identified in active forms in diseased PISF, but MMP-7 was less prominent. MMP inhibitors, potential future tissue protective drugs, seemingly do not interfere with the defensive antibacterial action of MMP-7.

Inhibition of matrix metalloproteinases by chemically modified tetracyclines in sepsis

Sepsis precipitates a systemic inflammatory stimulus that causes systemic release of cytokines and sequestration of polymorphonuclear neutrophils, resulting in degranulation of matrix metalloproteinases (MMPs), which causes extracellular matrix basement membrane degradation. One of the important anti-inflammatory properties of tetracyclines is their ability to inhibit MMPs. In this study, we focused on the regulation of MMPs in sepsis and their reduction by treatment with nonantimicrobial chemically modified tetracyclines (CMTs), which retain their anti-inflammatory activity. Sepsis was induced by cecal ligation and puncture (CLP) method. At 24 h and 1 h before CLP, some rats received CMT-3 (25 mg/kg), another group of rats received hydroxamate (H; an inhibitor of MMP; 25 mg/kg), and untreated rats received saline by gavage. At 0 h, 0.5 h, 1.5 h, and 24 h after CLP, blood and liver samples were collected. Plasma and liver MMP-9 by zymography and Western immunoblotting, plasma nitric oxide by measuring nitrate level, plasma glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) by enzymatic method, and liver gelatinase by radiolabeled gelatin lysis assay and 24 h mortality were determined. Plasma MMP-9 (92 kDa), nitrate, and GOT and GPT levels were elevated compared with the time 0 level and reached peak at 1.5 h CLP and remained high for 24 h. Both CMT-3 and H treatment reduced GOT,GPT, 92-kDa gelatinase, and nitrate levels throughout the 24 h. CMT-3 and H are equally effective in sepsis treatment. The 24-h mortality for CLP rats was 30%, whereas pretreatment with CMT-3 and H resulted in 0% mortality. Hepatic MMP-9 and gelatinase activity increased significantly after CLP, and pretreatment with CMT-3 and H inhibited these expressions. These results indicate the beneficial effect of CMT-3 in preventing the increase in GOT, GPT, NO, MMP-9, gelatinase activity, and the ensuing septic shock.

Inhibition of matrix metalloproteinase-14 in osteosarcoma cells by clodronate

BACKGROUND

Bisphosphonates reduce the bone metastasis formation and angiogenesis but the exact molecular mechanisms involved are unclear. Progelatinase A (proMMP-2; 78 KDa) is activated up during the tumor spread and metastasis by a cell surface-associated matrix metalloproteinase (membrane-type matrix metalloproteinase [MT1-MMP] or MMP-14).

MATERIAL AND METHODS

We evaluated the effects of a bisphosphonate (clodronate) on MT1-MMP mRNA expression and protein production, catalytic activity and proteolytic activation of proMMP-2 by cultured human MG-63 osteosarcoma cells.

RESULTS

Clodronate, at therapeutically attainable noncytotoxic concentrations, dose-dependently inhibited phorbol myristic acetate (PMA)-induced proteolytic activation of proMMP-2 by human MG-63 osteosarcoma cells. Clodronate also downregulated the PMA-induced expression of MT1-MMP mRNA and protein production in human MG-63 osteosarcoma cells, as evidenced by Northern analysis and fluorescent immunohistochemistry. Furthermore, clodronate inhibited directly and dose-dependently MT1-MMP activity, and the MT1-MMP inhibition by clodronate was reduced in the presence of an increased (5 mM) Ca(2+) concentrations when compared to physiological (1 mM) Ca(2+) concentrations.

CONCLUSION

We conclude that (1) the extracellular/cell-associated mechanism of bisphosphonate involves inhibition of MT1-MMP catalytic activity eventually by chelation, and that (2) intracellular mechanism involves downregulation of induced MT1-MMP mRNA and protein expression. The inhibition and downregulation of MT1-MMP by clodronate can be related to their ability to reduce MG-63 osteosarcoma cell invasion and spread. These findings may, at least in part, explain at molecular level the antitumor and antibone resorption activities of clodronate observed in clinical studies.

Inhibition of collagenase and metalloproteinases by aloins and aloe gel

The effects of Aloe barbadensis gel and aloe gel constituents on the activity of microbial and human metalloproteinases have been investigated. Clostridium histolyticum collagenase (ChC) results dose-dependently inhibited by aloe gel and the activity-guided fractionation led to an active fraction enriched in phenolics and aloins. Aloins have been shown to be able to bind and to inhibit ChC reversibly and non-competitively. Aloe gel and aloins are also effective inhibitors of stimulated granulocyte matrix metalloproteinases (MMPs). The remarkable structural resemblances between aloins and the pharmacophore structure of inhibitory tetracyclines, suggest that the inhibitory effects of aloins are via an interaction between the carbonyl group at C(9) and an adjacent hydroxyl group of anthrone (C(1) or C(8)) at the secondary binding site of enzyme, destabilizing the structure of granulocyte MMPs.