Specificity of the anticollagenase action of tetracyclines: relevance to their anti-inflammatory potential

Identifying platelet-derived factors as amplifiers of B. burgdorferi-induced cytokine production

Previous studies have shown that monocytes can be 'trained' or tolerized by certain stimuli to respond stronger or weaker to a secondary stimulation. Rewiring of glucose metabolism was found to be important in inducing this phenotype. As we previously found that Borrelia burgdorferi (B. burgdorferi), the causative agent of Lyme borreliosis (LB), alters glucose metabolism in monocytes, we hypothesized that this may also induce long-term changes in innate immune responses. We found that exposure to B. burgdorferi decreased cytokine production in response to the TLR4-ligand lipopolysaccharide (LPS). In addition, B. burgdorferi exposure decreased baseline levels of glycolysis, as assessed by lactate production. Using GWAS analysis, we identified a gene, microfibril-associated protein 3-like (MFAP3L) as a factor influencing lactate production after B. burgdorferi exposure. Validation experiments proved that MFAP3L affects lactate- and cytokine production following B. burgdorferi stimulation. This is mediated by functions of MFAP3L, which includes activating ERK2 and through activation of platelet degranulation. Moreover, we showed that platelets and platelet-derived factors play important roles in B. burgdorferi-induced cytokine production. Certain platelet-derived factors, such chemokine C-X-C motif ligand 7 (CXCL7) and (C-C motif) ligand 5 (CCL5), were elevated in the circulation of LB patients in comparison to healthy individuals.

The tetrapartite synapse in neuropsychiatric disorders: Matrix metalloproteinases (MMPs) as promising targets for treatment and rational drug design

Inflammation and an exacerbated immune response are widely accepted contributing mechanisms to the genesis and progression of major neuropsychiatric disorders. However, despite the impressive advances in understanding the neurobiology of these disorders, there is still no approved drug directly linked to the regulation of inflammation or brain immune responses. Importantly, matrix metalloproteinases (MMPs) comprise a group of structurally related endopeptidases primarily involved in remodeling extracellular matrix (ECM). In the central nervous system (CNS), these proteases control synaptic plasticity and strength, patency of the blood-brain barrier, and glia-neuron interactions through cleaved and non-cleaved mediators. Several pieces of evidence have pointed to a complex scenario of MMPs dysregulation triggered by neuroinflammation. Furthermore, major psychiatric disorders' affective symptoms and neurocognitive abnormalities are related to MMPs-mediated ECM changes and neuroglia activation. In the past decade, research efforts have been directed to broad-spectrum MMPs inhibitors with frustrating clinical results. However, in the light of recent advances in combinatorial chemistry and drug design technologies, specific and CNS-oriented MMPs modulators have been proposed as a new frontier of therapy for regulating ECM properties in the CNS. Therefore, here we aim to discuss the state of the art of MMPs and ECM abnormalities in major neuropsychiatric disorders, namely depression, bipolar disorder, and schizophrenia, the possible neuro-immune interactions involved in this complex scenario of MMPs dysregulation and propose these endopeptidases as promising targets for rational drug design.

Combining Ceftriaxone with Doxycycline and Daptomycin Reduces Mortality, Neuroinflammation, Brain Damage, and Hearing Loss in Infant Rat Pneumococcal Meningitis

Despite appropriate antibiotic therapy, pneumococcal meningitis (PM) is associated with a case fatality rate of up to 30% in high-income countries. Survivors often suffer from severe lifelong disabilities. An excessive inflammatory reaction drives the pathophysiology, leading to brain damage and neurologic sequelae. We aimed to improve the outcome of experimental PM by simultaneously targeting different pathophysiological mechanisms with combined adjunctive therapies previously shown to be neuroprotective. In vitro, the anti-inflammatory effects of doxycycline and daptomycin were evaluated on primary rat astroglial cells stimulated with Streptococcus pneumoniae Eleven-day-old infant Wistar rats were infected intracisternally with S. pneumoniae and randomized for treatment with ceftriaxone or combination adjuvant therapy consisting of ceftriaxone, daptomycin, and doxycycline. During acute PM, combined-adjuvant therapy with ceftriaxone, daptomycin, and doxycycline increased the survival rate from 64.1% to 85.8% (P < 0.01) and alleviated weight loss compared to ceftriaxone monotherapy (P < 0.01). Levels of inflammatory cytokines were significantly reduced by combined-adjuvant therapy in vitro (P < 0.0001) and in cerebrospinal fluid in vivo (P < 0.05). In infected animals treated with combined adjunctive therapy, cortical damage was significantly reduced (P < 0.05), and animals showed a trend toward better hearing capacity 3 weeks after the infection (P = 0.089), an effect which was significant in mildly infected animals (48 decibels [dB] versus 67.22 dB; P < 0.05). These mildly infected animals showed significantly reduced cochlear fibrous occlusion (P < 0.01). By combining nonbacteriolytic daptomycin and anti-inflammatory doxycycline with ceftriaxone, the previously reported beneficial effects of the drugs were cumulated and identified the triple-antibiotic therapy as a promising therapeutic option for pediatric PM.

Adjunctive Effects of a Sub-Antimicrobial Dose of Doxycycline on Clinical Parameters and Potential Biomarkers of Periodontal Tissue Catabolism

Objectives: The aim of the present randomized, double-blind, placebo-controlled, parallel-arm study was to examine the effectiveness of a sub-antimicrobial dose of doxycycline (SDD) in combination with nonsurgical periodontal therapy, compared to nonsurgical periodontal therapy alone, on potential gingival crevicular fluid (GCF) biomarkers of periodontal tissue catabolism related to the clinical outcomes over a 12-month period. Materials and Methods: GCF was collected and clinical parameters were recorded from 30 periodontitis patients randomized either to an SDD or placebo group. The SDD group received SDD (20 mg) b.i.d for 3 months plus scaling and root planing (SRP), while the placebo group was given placebo capsules b.i.d for 3 months plus SRP. The patients were evaluated every 3 months during the 12-month study period. At each visit, clinical parameters and GCF sampling were repeated. Matrix metalloproteinase (MMP)-8, MMP-9, MMP-13, myeloperoxidase (MPO), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase-5 (TRAP-5) were determined by IFMA and ELISA. Results: Significant improvements were observed in all clinical parameters in both groups over 12 months (p < 0.0125) while the SDD group showed significantly better reduction in gingival index (GI) and pocket depth and a gain in clinical attachment compared to the placebo group (p < 0.05). GCF MMP-8 and OPG levels significantly reduced in the SDD group compared to baseline (p < 0.05). GCF MMP-9 significantly decreased in both groups compared to baseline (p < 0.05). GCF MPO significantly decreased at 3 and 9 months in the SDD group, while it significantly decreased at 6 months in the placebo group (p < 0.05). TRAP and MMP-13 could be detected in none of the samples. Conclusions: The present results indicate that three months of adjunctive usage of SDD to nonsurgical periodontal therapy compared to nonsurgical periodontal therapy alone in periodontitis patients results in further improvement of clinical periodontal parameters and GCF markers of periodontal tissue breakdown over a 12-month period. Beneficial effects of adjunctive SDD therapy is likely to be related to the reduced levels of two major periodontitis-associated MMPs, MMP-8 and -9, and their potential oxidative activator MPO.

Association study of MMP8 gene in osteoarthritis

OBJECTIVES

Osteoarthritis (OA) is a joint disease common in the elderly. There is a prior functional evidence for different matrix metalloproteinases (MMPs), such as MMP8 and MMP9, having a role in the breakdown of cartilage extracellular matrix in OA. Thus, we analyzed whether the common genetic variants of MMP8 and MMP9 contribute to the risk of OA.

MATERIALS AND METHODS

In total, 13 common tagging single-nucleotide polymorphisms (SNPs) were studied in a discovery knee OA cohort of 185 cases and 895 controls. For validation, two knee OA replication cohorts and two hand OA replication cohorts were studied (altogether 1369 OA cases, 4445 controls in the five cohorts). The χ(2) test for individual study cohorts and Cochran-Mantel-Haenszel test for combined meta-analysis were calculated using Plink.

RESULTS

The rs1940475 SNP in MMP8 showed suggestive association in the discovery cohort (OR = 0.721, 95% CI 0.575-0.906; p = 0.005). Other knee and hand OA replication study cohorts showed similar trend for the predisposing allele without reaching statistical significance in independent replication cohorts nor in their meta-analysis (p > 0.05). Meta-analysis of all five hand and knee OA study cohorts yielded a p-value of 0.027 (OR = 0.904, 95% CI 0.826-0.989).

CONCLUSIONS

Initial analysis of the MMP8 gene showed suggestive association between rs1940475 and knee OA, but the finding did not replicate in other study cohorts, even though the trend for predisposing allele was similar in all five cohorts. MMP-8 is a good biological candidate for OA, but our study did not find common variants with significant association in the gene.

The immune response and antibacterial therapy

The host's immune defence mechanisms are indispensable factors in surviving bacterial infections. However, in many circumstances, the immune system alone is inadequate. Since the 1940s, the use of antibacterial therapy has saved millions of lives, improving the span and quality of life of individuals. Unfortunately, we are now facing an era where antibacterial agents are threatened by resistance. In addition to targeting bacteria, some antibacterial agents affect various aspects of the immune response to infection. Since many antibacterial drugs are failing in efficacy due to resistance, it has been strongly suggested that any synergy between these drugs and the immune response be exploited in the treatment of bacterial infections. This review explores the influence of antibacterial therapy on the immune response and new approaches that could exploit this interaction for the treatment of bacterial infections.

Doxycycline inhibits polarization of macrophages to the proangiogenic M2-type and subsequent neovascularization

Macrophages occur along a continuum of functional states between M1-type polarized macrophages with antiangiogenic and antitumor activity and M2-type polarized macrophages, which have been implicated to promote angiogenesis and tumor growth. Proangiogenic M2-type macrophages promote various pathologic conditions, including choroidal neovascularization in models of neovascular age-related macular degeneration, or certain cancers, such as glioblastoma multiforme. Thus, a potential novel therapeutic approach to target pathological angiogenesis in these conditions would be to inhibit the polarization of macrophages toward the proangiogenic M2-type. However, no pharmacological inhibitors of M2-type macrophage polarization have been identified yet. Here we performed an unbiased pharmacological and small chemical screen to identify drugs that inhibit proangiogenic M2-type macrophage polarization and block pathologic macrophage-driven neovascularization. We identified the well tolerated and commonly used antibiotic doxycycline as a potent inhibitor of M2-type polarization of macrophages. Doxycycline inhibited, in a dose-dependent manner, M2-type polarization of human and bone marrow-derived mouse macrophages without affecting cell viability. Furthermore, doxycycline inhibited M2-type macrophage polarization and subsequent neovascularization in vivo in a laser injury model of choroidal neovascularization. Thus, doxycycline could be used to enhance current antiangiogenic treatment approaches in various conditions that are promoted by proangiogenic M2-type macrophages, including neovascular age-related macular degeneration and certain cancers.

Peripheral ulcerative keratitis: Our challenging experience

A 52 year old male presented with peripheral ulcerative keratitis in the right eye. Patient's history included retinitis pigmentosa, pseudophakia (right eye), cataract (left eye), bilateral partial deafness, ischemic heart disease, hypertension, type 1 diabetes mellitus, depression, hyperparathyroidism, hypertriglycemia and renal failure. The patient was on weekly hemodialysis. The peripheral corneal ulceration remained stable until he developed sudden and rapid thinning after eight months of regular follow up and management. Laboratory investigations including immunological studies were negative and we had to rely on treatment based on clinical signs, including the visual acuity, size, depth and staining of the ulcer and perilimbal, episcleral, scleral, corneal and anterior chamber reactions. The patient was treated with medical and conservative approaches and the eye was protected with a plastic shield to avoid injury. Despite our efforts, the patient perforated his eye due to a trivial trauma during sleep. He was managed successfully with cyanoacrylate glue and a bandage contact lens. The anterior chamber reformed after the perforation was sealed and the patient is on a regular follow up with a multidisciplinary approach.

The enhanced permeability retention effect: a new paradigm for drug targeting in infection

Multidrug-resistant, Gram-negative infection is a major global determinant of morbidity, mortality and cost of care. The advent of nanomedicine has enabled tailored engineering of macromolecular constructs, permitting increasingly selective targeting, alteration of volume of distribution and activity/toxicity. Macromolecules tend to passively and preferentially accumulate at sites of enhanced vascular permeability and are then retained. This enhanced permeability and retention (EPR) effect, whilst recognized as a major breakthrough in anti-tumoral targeting, has not yet been fully exploited in infection. Shared pathophysiological pathways in both cancer and infection are evident and a number of novel nanomedicines have shown promise in selective, passive, size-mediated targeting to infection. This review describes the similarities and parallels in pathophysiological pathways at molecular, cellular and circulatory levels between inflammation/infection and cancer therapy, where use of this principle has been established.

Effect of doxycycline in patients of moderate to severe chronic obstructive pulmonary disease with stable symptoms

BACKGROUND:

The protease-antiprotease hypothesis proposes that inflammatory cells and oxidative stress in chronic obstructive pulmonary disease (COPD) produce increased levels of proteolytic enzymes (neutrophil elastase, matrix metalloproteinases [MMP]) which contribute to destruction of parenchyma resulting in progressive decline in forced expiratory volume in one second. Doxycycline, a tetracycline analogue, possesses anti-inflammatory properties and inhibits MMP enzymes.

OBJECTIVES:

To assess the effect of 4 weeks doxycycline in a dose of 100 mg once a day in patients of moderate to severe COPD with stable symptoms.

METHODS:

In an interventional, randomized, observer-masked, parallel study design, the effect of doxycycline (100 mg once a day for 4 weeks) was assessed in patients of COPD having stable symptoms after a run-in period of 4 weeks. The study participants in reference group did not receive doxycycline. The parameters were pulmonary functions, systemic inflammation marker C-reactive protein (CRP), and medical research council (MRC) dyspnea scale. Use of systemic corticosteroids or antimicrobial agents was not allowed during the study period.

RESULTS:

A total of 61 patients completed the study (31 patients in doxycycline group and 30 patients in reference group). At 4 weeks, the pulmonary functions significantly improved in doxycycline group and the mean reduction in baseline serum CRP was significantly greater in doxycycline group as compared with reference group. There was no significant improvement in MRC dyspnea scale in both groups at 4 weeks.

CONCLUSION:

The anti-inflammatory and MMP-inhibiting property of doxycycline might have contributed to the improvement of parameters in this study.

Late complications of clinical clostridium histolyticum collagenase use in Dupuytren's disease

Introduction

While Dupuytren's disease can cause disabling contractures requiring open surgery, a less-invasive option using Clostridium Histolyticum collagenase (CHC) via percutaneous injection was recently reported. A recent prospective, randomized trial demonstrated few complications during 90 days follow-up, however did not assess any longer term follow-up for these patients. Long-term outcomes in this setting have not been adequately reported, and the current manuscript aims to identify late complications from the clinical use of percutaneous CHC.

Methods

The current manuscript reports an extended 12-month follow-up for a cohort of twelve of patients enrolled in the original prospective, randomized trial, treated at a single institution. An analysis of complications requiring surgical intervention was undertaken.

Results

Two of twelve patients reported debilitating pain and triggering requiring surgical intervention. Extensive deep-tissue scarring and adhesions were identified, providing the first visual and qualitative analysis of the pathologic effects of CHC.

Conclusion

Late complications from CHC use can and have occurred, outside the follow-up period of the initial phase III trials. Longer term follow-up of such patients is thus essential, and further investigation and characterization of the late effects of CHC use is warranted.

Odontogenic keratocysts/keratocystic odontogenic tumours: biological characteristics, clinical manifestation and treatment

BACKGROUND

Odontogenic keratocysts (OKCs) now reclassified as Keratocystic odontogenic tumours (KCOTs) are a clinical entity with a characteristic microscopic picture, kinetic growth and biological behaviour. They arise from the proliferation of the epithelial dental lamina in both maxilla and mandible and occur in patients of all ages. 70-80% of keratocysts are found in the mandible commonly in the angle between the jaw and mandibular branch and maxillary region of the third molar. The cysts are long latent, often symptomless and may attain remarkable dimensions without significant deformation of the jaw bones. They are often found during routine dental X-ray examination. Compared to other types of jaw cyst, odontogenic cysts have a striking tendency to rapid growth and re-occurrence.

AIMS

This review focuses on the biological characteristics, clinical behaviour and treatment of KCOTs.

METHODS

The databases searched were the PubMed interface of MEDLINE and LILACS.

RESULTS AND CONCLUSIONS

Ondontogenic keratinocysts are not currently a diagnostic problem. Orthopantomograms which are today ordinary tools of dental investigation enable diagnosis of clinically asymptomatic cystic lesions. The problem remains the optimal therapeutic approach to reduce the still high likelihood of postoperative recurrence. There is no complete consensus on the ideal operating procedure but cystectomy with delayed extirpation is favoured. An open question also remains the timeliness of screening for postoperative recurrences. Given that the first clinical manifestation of Nevoid Basal Cell Carcioma Syndome (NBCCS) may be lesions of this type, routine histopathological classification supplemented by analysis of immunophenotype should be done. Patients with proven sporadic and especially syndromic OKC should be long term screened. In patients with NBCC preventive X ray examination is recommended only once a year.

Imaging the impact of chemically inducible proteins on cellular dynamics in vivo

The analysis of dynamic events in the tumor microenvironment during cancer progression is limited by the complexity of current in vivo imaging models. This is coupled with an inability to rapidly modulate and visualize protein activity in real time and to understand the consequence of these perturbations in vivo. We developed an intravital imaging approach that allows the rapid induction and subsequent depletion of target protein levels within human cancer xenografts while assessing the impact on cell behavior and morphology in real time. A conditionally stabilized fluorescent E-cadherin chimera was expressed in metastatic breast cancer cells, and the impact of E-cadherin induction and depletion was visualized using real-time confocal microscopy in a xenograft avian embryo model. We demonstrate the assessment of protein localization, cell morphology and migration in cells undergoing epithelial-mesenchymal and mesenchymal-epithelial transitions in breast tumors. This technique allows for precise control over protein activity in vivo while permitting the temporal analysis of dynamic biophysical parameters.

Injectable collagenase Clostridium histolyticum: a new nonsurgical treatment for Dupuytren's disease

PURPOSE

The Collagenase Option for the Reduction of Dupuytren's (CORD) II study investigated the efficacy and safety of injectable Xiaflex (collagenase clostridium histolyticum), in patients with Dupuytren's contracture.

METHODS

This was a prospective, randomized, placebo-controlled trial with 90-day double-blind and 9-month open-label phases. We randomized patients with contractures affecting metacarpophalangeal (MCP) or proximal interphalangeal (PIP) joints 2 to 1 to collagenase (0.58 mg) or placebo. Cords received a maximum of 3 injections. Cord disruption was attempted the day after injection using a standardized finger extension procedure. Primary end point was reduction in contracture to 0° to 5° of normal 30 days after the last injection.

RESULTS

We enrolled 66 patients; 45 cords (20 MCP to 25 PIP joints) received collagenase and 21 cords (11 MCP to 10 PIP joints) received placebo in the double-blind phase. Statistically significantly more cords injected with collagenase than placebo met the primary end point (44.4% vs 4.8%; p <. 001). The mean percentage decrease in degree of joint contracture from baseline to 30 days after last injection was 70.5% ± 29.2% in the collagenase group and 13.6% ± 26.1% in the placebo group (p < .001). The mean increase in range of motion was significantly greater in the collagenase (35.4° ± 17.8°) than in the placebo (7.6° ± 14.9°; p < .001) group. Efficacy after open-label treatment was similar to that after the double-blind phase: 50.7% of all joints achieved 0° to 5° of normal. More patients were satisfied with collagenase (p < .001). No joint had recurrence of contracture. One patient had a flexion pulley rupture and one patient underwent routine fasciectomy to address cord proliferation and sensory abnormality. No tendon ruptures or systemic allergic reactions were reported. Most adverse events were related to the injection or finger extension procedure.

CONCLUSIONS

Collagenase clostridium histolyticum is the first Food and Drug Administration-approved, nonsurgical treatment option for adult Dupuytren's contracture patients with a palpable cord that is highly effective and well tolerated.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic I.

Collagenase clostridium histolyticum for Dupuytren's contracture

IMPORTANCE OF THE FIELD

Dupuytren's disease is a non-malignant, progressive disorder of the hands that can severely limit hand function and diminish overall quality of life. With global life expectancy increasing, the prevalence of this disease appears to be increasing amongst all ethnic groups. Treatment has traditionally remained surgical with few effective, nonsurgical options. However, with the introduction of collagenase clostridium histolyticum to treat Dupuytren's contractures, physicians and surgeons may be provided with a new, office-based, non-surgical option to treat this disease.

AREAS COVERED IN THIS REVIEW

The literature behind the use of collagenase to treat Dupuytren's disease; including its mechanism of action, safety, efficacy and clinical evidence behind its recent FDA approval.

WHAT THE READER WILL GAIN

The latest information available on collagenase through a comprehensive review of PubMed and the websites of licensing organizations for medicinal products.

TAKE HOME MESSAGE

Phase III, clinical trials on collagenase for treatment of Dupuytren's contractures have recently been completed. Meeting primary and secondary objectives, collagenase has obtained FDA approval for clinical use. Collagenase now provides a non-operative option for Dupuytren's disease. Although short-term results show that collagenase is safe and efficacious, long-term effects of repeat injections and contracture recurrence rates have yet to be examined.

Attacking the multi-tiered proteolytic pathology of COPD: new insights from basic and translational studies

Protease activity in inflammation is complex. Proteases released by cells in response to infection, cytokines, or environmental triggers like cigarette smoking cause breakdown of the extracellular matrix (ECM). In chronic inflammatory diseases like chronic obstructive pulmonary disease (COPD), current findings indicate that pathology and morbidity are driven by dysregulation of protease activity, either through hyperactivity of proteases or deficiency or dysfunction their antiprotease regulators. Animal studies demonstrate the accuracy of this hypothesis through genetic and pharmacologic tools. New work shows that ECM destruction generates peptide fragments active on leukocytes via neutrophil or macrophage chemotaxis towards collagen and elastin derived peptides respectively. Such fragments now have been isolated and characterized in vivo in each case. Collectively, this describes a biochemical circuit in which protease activity leads to activation of local immunocytes, which in turn release cytokines and more proteases, leading to further leukocyte infiltration and cyclical disease progression that is chronic. This circuit concept is well known, and is intrinsic to the protease-antiprotease hypothesis; recently analytic techniques have become sensitive enough to establish fundamental mechanisms of this hypothesis, and basic and clinical data now implicate protease activity and peptide signaling as pathologically significant pharmacologic targets. This review discusses targeting protease activity for chronic inflammatory disease with special attention to COPD, covering important basic and clinical findings in the field; novel therapeutic strategies in animal or human studies; and a perspective on the successes and failures of agents with a focus on clinical potential in human disease.

Doxycycline inhibits vascular leakage and prevents ovarian hyperstimulation syndrome in a murine model

OBJECTIVE

To determine whether doxycycline would inhibit the development of ovarian hyperstimulation syndrome (OHSS) in a murine model.

DESIGN

Testing the effect of oral doxycycline treatment on gonadotropin-induced peritoneal capillary leakage in mice.

SETTING

Animal research facility.

ANIMAL(S)

Four-week-old female C57Bl/6 mice.

INTERVENTION(S)

Ovarian hyperstimulation syndrome was induced in mice by administering gonadotropins for 3 days followed by human chorionic gonadotropin. Peritoneal vascular leakage was quantified using the Miles vascular permeability assay. Mice were treated with daily oral doxycycline or vehicle.

MAIN OUTCOME MEASURE(S)

The concentration of dye in abdominal fluid extracted by peritoneal lavage was measured spectrophotometrically. Ascites volume was determined using dye dilution.

RESULT(S)

Doxycycline inhibited peritoneal vascular leakage and ascites accumulation in the hormonally stimulated mice. Doxycycline treatment did not inhibit ovarian stimulation or ovulation when compared with controls, as indicated by similar ovarian morphology, ovarian weights, and corpora lutea counts. Importantly, vessel density within the corpora lutea was similar in the two groups.

CONCLUSION(S)

Doxycycline prevents OHSS in a murine model without compromising ovarian stimulation. This effect is caused by inhibition of vascular leakage. Doxycycline's potential in preventing human OHSS is promising and warrants further studies.

Doxycycline induces membrane expression of VE-cadherin on endothelial cells and prevents vascular hyperpermeability

The endothelium lining blood vessels serves as a barrier against vascular hyperpermeability, and its maintenance is critical to organ health. Inflammatory mediators evoke tissue edema by disrupting the expression of membrane junctional proteins, which mediate binding between endothelial cell membranes. Endothelial cell-cell junctions form a diffusion barrier between the intravascular and interstitial space. To prevent the morbidity and mortality caused by exaggerated vascular permeability associated with pathological states (e.g., inflammatory and hypersensitivity disorders, pulmonary edema, traumatic lung injury, cerebral edema resulting from stroke, and others), it is important to develop therapeutic approaches to stabilize these interendothelial junctions. Vascular endothelial growth factor (VEGF), a potent proangiogenic cytokine, was first described as vascular permeability factor (VPF). Doxycycline, a tetracycline derivative, has been shown to inhibit angiogenesis in both humans and animal models. We now report that oral doxycycline prevents VPF/VEGF-induced vascular permeability, interleukin-2-induced pulmonary edema, and delayed-type hypersensitivity (DTH) in mice. Remarkably, doxycycline also inhibits tumor growth and tumor-associated vascular hyperpermeability. Finally, we show that doxycycline targets the adherens junction in vascular endothelial cells by inducing the total amount of VE-cadherin expression while decreasing the degree of its phosphorylation. The potential of doxycyline as a therapeutic inhibitor of vascular hyperpermeability in human clinical conditions is promising and warrants further studies.

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.

Doxycycline reduces mortality and injury to the brain and cochlea in experimental pneumococcal meningitis

Bacterial meningitis is characterized by an inflammatory reaction to the invading pathogens that can ultimately lead to sensorineural hearing loss, permanent brain injury, or death. The matrix metalloproteinases (MMPs) and tumor necrosis factor alpha-converting enzyme (TACE) are key mediators that promote inflammation, blood-brain barrier disruption, and brain injury in bacterial meningitis. Doxycycline is a clinically used antibiotic with anti-inflammatory effects that lead to reduced cytokine release and the inhibition of MMPs. Here, doxycycline inhibited TACE with a 50% inhibitory dose of 74 microM in vitro and reduced the amount of tumor necrosis factor alpha released into the cerebrospinal fluid by 90% in vivo. In an infant rat model of pneumococcal meningitis, a single dose of doxycycline (30 mg/kg) given as adjuvant therapy in addition to ceftriaxone 18 h after infection significantly reduced the mortality, the blood-brain barrier disruption, and the extent of cortical brain injury. Adjuvant doxycycline (30 mg/kg given subcutaneously once daily for 4 days) also attenuated hearing loss, as assessed by auditory brainstem response audiometry, and neuronal death in the cochlear spiral ganglion at 3 weeks after infection. Thus, doxycycline, probably as a result of its anti-inflammatory properties, had broad beneficial effects in the brain and the cochlea and improved survival in this model of pneumococcal meningitis in infant rats.

Tear fluid levels of MMP-8 are elevated in ocular rosacea--treatment effect of oral doxycycline

BACKGROUND

Ocular rosacea (OcR) is a chronic inflammatory disease especially affecting lid margins. Previous studies have shown that it is accompanied by increased levels and activation of tear fluid gelatinases. Matrix metalloproteinase 8 (MMP-8; collagenase 2) levels and activation are commonly elevated in many inflammatory conditions. Therefore we studied here whether MMP-8 concentration and activation in tear fluid are increased also in OcR, and if an oral doxycycline regimen could rectify the situation.

METHODS

Tear fluid samples were collected from 22 OcR patients and 22 healthy controls. The OcR patients were then treated with an oral doxycycline regimen for 8 weeks and tear fluid samples collected again after 4 and 8 weeks. Conjunctival brush cytology and patients' subjective symptoms were scored. MMP-8 concentrations in the tear fluid were assessed by immunofluorometric assay and the molecular forms and isoenzyme expression of MMP-8 were studied by Western immunoblotting.

RESULTS

The mean MMP-8 concentration was statistically significantly higher in OcR (156.8+/-207.4 mug/ml) than in the normal subjects (53.5+/-66.7 mug/ml) (P=0.036), but decreased to 79.2+/-141.6 mug/l and 53.6+/-75.2 mug/l after 4 and 8 weeks doxycycline treatment, respectively. There was a statistically significant difference between the untreated OcR and the MMP-8 results after 4 or 8 weeks of oral doxycycline (P=0.041 and 0.069, respectively) and the OcR patients experienced statistically significant relief of their subjective symptoms (P=0.0001) after the doxycycline regimen. Both the normal and OcR tear fluid contained the larger, 60-80 kDa highly- glycosylated polymorphonuclear leukocyte-type MMP-8 isoform in Western immunoblotting, but not the 45-55 kDa less glycosylated mesenchymal-type isoform. MMP-8 activation was in practice present only in the OcR samples, and was inhibited by oral doxycycline.

CONCLUSIONS

MMP-8 concentration and activation degree in tear fluid are increased in OcR, probably reflecting increased inflammatory activity. Doxycycline effectively reduces these pathologically excessive levels and activation of MMP-8, and relieves patients' subjective symptoms.

The effect of adjunctive low-dose doxycycline therapy on clinical parameters and gingival crevicular fluid matrix metalloproteinase-8 levels in chronic periodontitis

BACKGROUND

Low-dose doxycycline (LDD) is recognized to have non-antimicrobial properties that can therapeutically modulate the host response. The aim of the present randomized, double-blind, placebo-controlled, parallel-arm study was to examine the effectiveness of LDD in combination with non-surgical periodontal therapy, compared to non-surgical periodontal therapy alone, on gingival crevicular fluid (GCF) matrix metalloproteinase-8 (MMP-8) levels and clinical parameters over a 12-month period in patients with chronic periodontitis.

METHODS

GCF samples were collected, and clinical parameters including probing depth (PD), clinical attachment level, gingival index (GI), and plaque index were recorded. Thirty chronic periodontitis patients were randomized either to a low-dose doxycycline (LDD) or placebo group. The LDD group received low-dose doxycycline (20 mg) b.i.d. for 3 months plus scaling and root planing (SRP), while the placebo group was given placebo capsules b.i.d. for 3 months plus SRP. The patients were evaluated every 3 months during the 12-month study period. At each visit, all clinical measurements and GCF sampling were repeated. GCF MMP-8 levels were determined by a time-resolved immunofluorescence assay. Intragroup comparisons were tested by the Friedman test followed by Wilcoxon signed-rank test to analyze significance of changes over time. The Mann-Whitney test was used to determine differences between the LDD and placebo groups.

RESULTS

Significant improvements were observed in all clinical parameters in both groups over the 12-month period (P < 0.0125). The LDD group showed a significantly greater reduction in mean PD scores at 9 and 12 months and in mean GI scores at all time points than the placebo group (P < 0.05). From baseline to 12 months, GCF MMP-8 levels were significantly reduced in both groups (P < 0.0125). The GCF MMP-8 level in the LDD group was significantly lower than that of the placebo group at 6 months (P < 0.05).

CONCLUSIONS

The present results indicate that low-dose doxycycline therapy in combination with scaling and root planing can reduce GCF MMP-8 levels and improve clinical periodontal parameters in patients with chronic periodontitis. These results provide additional information about the usefulness of low-dose doxycycline therapy as an adjunct to non-surgical periodontal therapy in the long-term management of periodontal disease. The effectiveness and course of low-dose doxycycline therapy can be monitored conveniently by assessing GCF MMP-8 levels.

Bone defects of the facial skeleton - replacement with biomaterials

The authors report on their experience with bone defect treatment following surgery of jaw-bone cysts. This is based on the use of cadaveric ground spongiosis saturated with tetracycline and metronidazol solution. The study shows the above mentioned material is very suitable for bone defect therapy, and cost effective. The results were verified by clinical and X-ray examination.

Hypertonic induction of COX-2 expression in renal medullary epithelial cells requires transactivation of the EGFR

Hypertonic stress increases expression of cyclooxygenase-2 (COX-2) in renal medullary epithelial and interstitial cells. Because hypertonic COX-2 expression is, in part, sensitive to inhibition of the ERK MAPK, an effector of activated receptor tyrosine kinases such as the EGF receptor, we investigated a role for this receptor in signaling to COX-2 expression. Hypertonic stress increased COX-2 expression at the mRNA and protein levels at 6 and 24 h of hypertonic treatment. Two potent, specific inhibitors of the EGF receptor kinase, AG-1478 and PD-153035, abrogated this effect. These inhibitors also blocked the ability of hypertonic stress to increase PGE2 release; in addition, they partially blocked tonicity-dependent phosphorylation of ERK but not of the related MAPKs, JNK or p38. Pharmacological inhibition of ERK activation partially blocked tonicity-dependent COX-2 expression. Hypertonic induction of COX-2 was likely transcriptionally mediated, as NaCl stress increased luciferase reporter gene activity under control of the human COX-2 promoter, and this effect was also sensitive to inhibition of the EGF receptor kinase. Metalloproteinase action is required for transactivation of the EGF receptor. Pharmacological inhibition of metalloproteinase function blocked tonicity-inducible COX-2 expression. Furthermore, the effect of hypertonicity on COX-2 expression was also evident in the EGF-responsive Madin-Darby canine kidney and 3T3 cell lines but was virtually absent from the EGF-unresponsive (and EGF receptor null) Chinese hamster-derived CHO cell line. Taken together, these data indicate that hypertonicity-dependent COX-2 expression in medullary epithelial cells requires transactivation of the EGF receptor and, potentially, ectodomain cleavage of an EGF receptor ligand.

Laminin-5 gamma2-chain and collagenase-2 (MMP-8) in human peri-implant sulcular fluid

Laminin-5 (LN-5) is an important epithelial cell-derived structural and adhesive component in hemidesmosomes and basement membranes (BM). In peri-implant tissue, gingival BM underlies the junctional epithelium (JE) and reflects the peri-implant health. Matrix metalloproteinase-8 (MMP-8 or collagenase-2) is one of the key mediators of periodontal tissue destruction. Western immunoblotting with image analysis was used to quantitate the molecular forms of LN-5 gamma2-chain and MMP-8 in peri-implant sulcular fluid (PISF) from healthy and diseased implants. These observations were related to the recorded gingival (GI) and bone resorption (BR) indices of the studied sites. Altogether, 72 PISF samples from osseointegrated dental implants were examined. Significantly elevated levels of fragmented LN-5 gamma2-chain species (45 and 70 kDa) and MMP-8 immunoreactivities were observed in diseased PISF in relation to healthy PISF. The elevated levels of both LN-5 gamma2-chain 45 and 70 kDa fragments and MMP-8 in diseased PISF from peri-mucositis (BR = 0) and peri-implantitis (BR >/= 1) lesions strongly correlated with elevated GI. Low levels - almost comparable to those seen in healthy control PISF - were seen in PISF from peri-implantitis lesions (BR >/= 1) with no GI. Activation of 75 kDa neutrophil (PMN)-type proMMP-8 to 10 kDa lower-molecular-size active forms was especially detected in PISF from peri-implantitis with elevated GI. These cross-sectional findings indicate that elevated MMP-8 and LN-5 gamma2-chain fragment levels in PISF can reflect the active phase of the inflammatory peri-implant disease. Longitudinal studies are required to assess their use, either alone or in combination as molecular biochemical PISF markers, to predict the risk of progression of peri-implantitis, as well as to monitor the impact of treatment of the disease.

Doxycycline and tissue repair in rats

Iterations in collagen turnover are integral to tissue repair. Repair gone awry, as a result of excess collagen accumulation or degradation, can contribute to pathologic ventricular remodeling. Pharmacologic interventions that would attenuate either aspect of faulty repair have therefore attracted interest. Tetracyclines, which inhibit both collagen synthesis and degradation, as well as angiogenesis, may hold promise, unrelated to their antimicrobial properties, in this regard. Assessment of their potential in rodent hearts with experimental injury can be problematic, given the often microscopic nature of tissue repair and brief involvement of matrix metalloproteinases (MMPs). We therefore selected a subcutaneous model in which granulation and fibrous tissues form over several weeks in response to croton oil and where fibrous tissue is subsequently resorbed because of high levels of collagenolytic activity. Untreated rats were compared with those given daily oral doxycycline (40 mg/kg). We harvested pouch tissue and exudate weekly for 5 weeks to assess hydroxyproline concentration and MMP activity (gelatin substrate zymography) of pouch wall and mononuclear cell count of pouch exudate. At week 2, neovascularization in pouch wall was measured by means of intravenous infusion of carmine-red dye in gelatin. The resultant "vascular cast" was solubilized and dye content quantitated with the use of spectrophotometry. Serum was assayed weekly for type I collagen carboxyterminal telopeptide (ICTP), a marker of collagen degradation. During weeks 1 and 2 and compared with untreated controls, doxycycline-treated rats had attenuated pouch tissue weight, collagen concentration, MMP2 lytic activity and vascularity, and reduced exudate volume and mononuclear cells. In vitro, doxycycline inhibited tissue gelatinolytic activity in a dose-dependent manner. At weeks 4 and 5, pouches were larger and collagen concentration was higher in doxycycline-treated rats, and serum ICTP levels were reduced at weeks 3 and 4. During the initial phase of pouch development, doxycycline exerts an inhibitory effect on tissue formation, likely mediated through its attenuation of angiogenesis and modulations of collagen turnover. As repair proceeds in subsequent weeks, doxycycline retards collagen degradation and pouch resorption by inhibiting MMPs. Doxycycline offers a multifaceted pharmacologic profile with which to modify various aspects of tissue repair in the rat.

Mycoplasmal respiratory infections in small animals: 17 cases (1988-1999)

Seventeen cases (i.e., 14 dogs and three cats) were identified as having Mycoplasma spp. as the sole bacterial isolate cultured from airway washings in 224 cases evaluated for lower respiratory disease that was present in each case. Primary diagnoses included pneumonia (35.3%), airway collapse (35.3%), and bronchitis (29.4%). Fourteen cases had follow-up information available. Of these cases, eight showed resolution or improvement with antimycoplasmal drugs. Mycoplasma spp. is recognized as a primary cause of respiratory disease in several species, including humans. The relationship between Mycoplasma spp. and respiratory disease detected in some of these cases suggests some Mycoplasma spp. may act as primary pathogens in dogs and cats.

Induction of matrix metalloproteinase-8 in human fibroblasts by basic calcium phosphate and calcium pyrophosphate dihydrate crystals: effect of phosphocitrate

Although matrix metalloproteinase-8 (MMP-8) was regarded as the exclusive product of the neutrophils, recent studies have shown that it is also expressed in articular chondrocytes, rheumatoid synovial fibroblasts and endothelial cells. Our aim was to determine the expression of MMP-8 in human fibroblasts (HF) by reverse transcription/polymerase chain reaction (RT/PCR). Northern and Western blotting methods and MMP-8 activity assay. We have shown the expression of MMP-8 in HF and its dose-dependent upregulation by basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPPD) crystals which are markers of severe joint degeneration in osteoarthritis. These effects require new protein synthesis and are reversed by phosphocitrate (PC). The results also show that this fibroblast MMP-8 is distinct from the neutrophil MMP-8 and from the fibroblast MMP-1. These results indicate that MMP-8 may play a significant role in the pathogenic effects of the crystals in osteoarthritis.

Evaluation of collagenase activity, matrix metalloproteinase-8, and matrix metalloproteinase-13 in horses with chronic obstructive pulmonary disease

OBJECTIVES

To determine collagenase activity and evaluate matrix metalloproteinase (MMP)-8 and MMP-13 in horses with chronic obstructive pulmonary disease (COPD).

ANIMALS

12 horses with COPD and 12 healthy control horses.

PROCEDURE

Collagenase activity was determined by use of an assay for degradation of type-I collagen. Western immunoblot analysis was used to identify interstitial collagenases MMP-8 and MMP-13 in tracheal epithelial lining fluid (TELF). Immunocytochemistry and in situ hybridization were used to determine cellular expression of these 2 collagenases in cells in bronchoalveolar lavage fluid (BALF).

RESULTS

Collagenase activity was approximately 7 times higher in samples obtained from horses with COPD, compared with control horses. During stabling, horses with COPD had significantly higher collagenase activity than after being maintained on summer pasture, when activity was similar to that of control horses. Immunoreactivity of MMP-8 and MMP-13 was significantly increased in TELF of horses with COPD, compared with healthy horses. In TELF, a positive correlation was detected between immunoreactivity of MMP-8 and MMP-13 and the amount of degradation of type-I collagen. Macrophages and epithelial cells were the major cellular sources of MMP-8 and MMP-13.

CONCLUSIONS AND CLINICAL RELEVANCE

Increased collagenase activity in TELF indicates active ongoing disease and, thus, may reflect lung tissue changes in horses with COPD. Measurements of collagenase activity and MMP immunoreactivity may provide additional diagnostic tools to identify the active phase of chronic lung disease.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Interference of antibacterial agents with phagocyte functions: immunomodulation or "immuno-fairy tales"?

Professional phagocytes (polymorphonuclear neutrophils and monocytes/macrophages) are a main component of the immune system. These cells are involved in both host defenses and various pathological settings characterized by excessive inflammation. Accordingly, they are key targets for immunomodulatory drugs, among which antibacterial agents are promising candidates. The basic and historical concepts of immunomodulation will first be briefly reviewed. Phagocyte complexity will then be unravelled (at least in terms of what we know about the origin, subsets, ambivalent roles, functional capacities, and transductional pathways of this cell and how to explore them). The core subject of this review will be the many possible interactions between antibacterial agents and phagocytes, classified according to demonstrated or potential clinical relevance (e.g., neutropenia, intracellular accumulation, and modulation of bacterial virulence). A detailed review of direct in vitro effects will be provided for the various antibacterial drug families, followed by a discussion of the clinical relevance of these effects in two particular settings: immune deficiency and inflammatory diseases. The prophylactic and therapeutic use of immunomodulatory antibiotics will be considered before conclusions are drawn about the emerging (optimistic) vision of future therapeutic prospects to deal with largely unknown new diseases and new pathogens by using new agents, new techniques, and a better understanding of the phagocyte in particular and the immune system in general.

Tetracyclines for the treatment of rheumatoid arthritis

In this review the rationale for the possible beneficial effect of tetracycline derivatives for the treatment of rheumatoid arthritis is discussed. Early studies (Sanchez, Skinner et al. and Brown et al. ) and the two open trials of the 1980s are briefly discussed. The three double-blind studies conducted in the 1990s (Kloppenburg et al. , The Netherlands; the MIRA trial, USA and the O'Dell et al., USA) are described in detail. The baseline clinical and demographic data for these patients, as well as the efficacy and toxicity data are described in the text and summarised in tables. The long-term data of the O'Dell et al.'s trial is described. Finally, side effects not observed during the conduct of these trials, but reported to occur in other patients, for example those receiving minocycline for the treatment of acne, are also listed.

Minocycline for the treatment of rheumatoid arthritis

The scientific basis for the use of antibiotics (with special emphasis on tetracycline and its derivatives) in the treatment of RA is discussed. The data on efficacy and toxicity are presented. The possible place of tetracycline derivatives within the overall strategy of RA treatment is also presented.

Tetracycline inhibits the nitric oxide synthase activity induced by endotoxin in cultured murine macrophages

Here we investigate the effects of tetracycline base and of a semi-synthetic tetracycline derivative, doxycycline, on the induction of inducible nitric oxide synthase and, hence, on the production of nitric oxide (NO) by lipopolysaccharide in J774 macrophage cultured in vitro. The treatment of J774 line with tetracycline base (6.25-250 microM) or doxycycline (5-50 microM) dose-dependently decreased the lipopolysaccharide-stimulated (1 microg/ml) inducible NO synthase activity and, consequently, nitrite formation. For instance, the inhibition was 70% for tetracycline base at 250 microM and 68% for doxycycline at 50 microM. The inhibitory effect of tetracyclines was due neither to a reduction in the viability of the cells, studied as colorimetric 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay, nor to an indiscriminate inhibition of total protein synthesis, but to a specific decrease in inducible NO synthase protein content in the cells, as attested by the significant reduction of the expression of inducible NO synthase, assayed by sodium-dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. However, no effect of tetracyclines on inducible NO synthase mRNA accumulation could be demonstrated in lipopolysaccharide-stimulated macrophage line, suggesting that the inhibitory effect of tetracyclines on NO synthesis involves post-transcriptional events. The reduction in lipopolysaccharide-stimulated nitrite accumulation produced by tetracyclines was significantly less when they were applied 6 h after lipopolysaccharide and absent 12 h after lipopolysaccharide, indicating that tetracyclines modify an early event in inducible NO synthase activation operating after mRNA transcription. The findings presented in this study indicate that the modulation of NO synthesis is another possible pathway by which tetracyclines may function as anti-inflammatory compounds.

Pharmacological effect of tetracyclines on proteoglycanases from interleukin-1-treated articular cartilage

Based on previous in vivo and in situ studies showing that tetracyclines possess antidegenerative effects on cartilage in conjunction with a reduced proteoglycan (PG) loss from the extracellular matrix, we investigated the effects of doxycycline, minocycline and tetracycline on the degradation and biosynthesis of PGs by bovine articular cartilage explants, both in vitro and in situ. Doxycycline, minocycline and tetracycline dose dependently, although weakly, inhibited PG degrading matrix metalloproteinases (MMPs) in vitro, when tested at concentrations ranging from 1 to 100 microM. Ro 31-4724 proved to be a potent inhibitor of MMP proteoglycanases (IC50 value 1.5 nM). Only at a concentration of 100 microM did doxycycline and minocycline significantly inhibit the interleukin-1 (IL-1)-induced augmentation of PG loss from cartilage explants into the nutrient media. The tetracyclines did not modulate the IL-1-mediated reduced aggregability of PGs, whereas 10 microM Ro 31-4724 partially restored the aggregability of PGs ex vivo. Tetracycline even at this high concentration was ineffective. Compared to the effects of the MMP inhibitor Ro 31-4724, treatment with tetracyclines at therapeutic serum levels of 1 or 10 microM was minimal, with little or no effect on cartilage proteoglycanases and PG biosynthesis. In our experiments, tetracyclines and Ro 31-4724 at doses evaluated had no cytotoxic effects on chondrocytes.

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

There are at least nine tetracycline (TC) analogs (both antimicrobial and nonantimicrobial) with documented capacity to inhibit, both in vitro and in vivo, the connective tissue degrading activity of matrix metalloproteinases (MMPs). Of the three MMPs that can degrade native helical collagens, MMP-13 (initially identified as rat osteoblast and human breast cancer collagenase, and now known to also be expressed by human cartilage and bone cells) is the most sensitive to TC inhibition (IC50 values in vitro generally less than 1 microgram/mL); the TCs inhibit both the collagenolytic as well as the gelatinolytic activity of this enzyme. The IC50 for MMP-8 (neutrophil collagenase) in vitro ranges from 15 to 86 micrograms/mL depending on assay conditions and choice of TC, whereas inhibition of the fibroblast enzyme (MMP-1) generally requires levels in excess of 200 micrograms/mL (except for CMT-3). The TC compounds that are highly effective against MMP-13 in vitro are also highly inhibitory of glycosaminoglycan release from interleukin-1-stimulated cartilage explants in culture. The current data correlate well with: (i) literature values for TC inhibition of bone resorption by isolated osteoclasts; (ii) inhibition by TCs of avian tibial resorption in organ culture; and (iii) the dramatic ability of TCs to inhibit bone destruction in many rat models (rats have only MMP-8 and MMP-13, and no MMP-1). By carefully selecting a TC-based MMP inhibitor and controlling dosages, it should be possible to inhibit pathologically excessive MMP-8 and/or MMP-13 activity, especially that causing bone erosion, without affecting the constitutive levels of MMP-1 needed for tissue remodeling and normal host function; in this regard, three newly developed CMTs (especially CMT-8, and, to a lesser extent, CMT-3 and -7) appear to be most effective.

Matrix metalloproteinase-8 is expressed in rheumatoid synovial fibroblasts and endothelial cells. Regulation by tumor necrosis factor-alpha and doxycycline

Neutrophil collagenase (matrix metalloproteinase-8 or MMP-8) is regarded as being synthesized exclusively by polymorphonuclear neutrophils (PMN). However, in vivo MMP-8 expression was observed in mononuclear fibroblast-like cells in the rheumatoid synovial membrane. In addition, we detected MMP-8 mRNA expression in cultured rheumatoid synovial fibroblasts and human endothelial cells. Up-regulation of MMP-8 was observed after treatment of the cells with either tumor necrosis factor-alpha (10 ng/ml) or phorbol 12-myristate 13-acetate (10 nM). Western analysis showed a similar regulation at the protein level. The size of secreted MMP-8 was 50 kDa, which is about 30 kDa smaller than MMP-8 from PMN. Conditioned media from rheumatoid synovial fibroblasts contained both type I and II collagen degrading activity. However, degradation of type II collagen, but not that of type I collagen, was completely inhibited by 50 microM doxycycline, suggesting specific MMP-8 activity. In addition, doxycycline down-regulated MMP-8 induction, at both the mRNA and protein levels. Thus MMP-8 exerts markedly wider expression in human cells than had been thought previously, implying that PMN are not the only source of cartilage degrading activity at arthritic sites. The inhibition of both MMP-8 activity and synthesis by doxycycline provides an incentive for further studies on the clinical effects of doxycycline in the treatment of rheumatoid arthritis.

Human neutrophil collagenase MMP-8 in peri-implant sulcus fluid and its inhibition by clodronate

The exact molecular mechanisms of the loosening of a dental implant are not well-known. The characteristics of implant sulci are similar to those of periodontal sulci regarding gingival crevicular fluid (GCF) and peri-implant sulcular fluid (PISF). Proteolytic enzymes, matrix metalloproteinases (MMPs), participate in peri-implant tissue remodeling. Clodronate is a well-tolerated bisphosphonate-group drug currently used in bone-resorption-related diseases in humans. The mechanisms of bisphosphonate action are not clarified. Collagenase activity in diseased PISF was significantly higher than in the clinically healthy group. Immunoblotting disclosed that diseased PISF contained increased immunoreactives MMP-8 compared with the healthy PISF. The residual latent collagenase activity in the diseased PISF was activated by gold thioglucose and inhibited completely by 100 microM of doxycycline closely resembling pure neutrophil collagenase (MMP-8). The presence of MMP-8 in diseased but not in clinically healthy PISF may prove to be a useful biochemical indicator to monitor peri-implant health and disease. Pure human neutrophil collagenase (MMP-8) and the MMP-8 present in PISF and in the GCF of both loosening implants and periodontitis-affected teeth were efficiently inhibited in vitro by clodronate (50% inhibition [IC50] was achieved by 150 microM of clodronate), an osteoactive, antiresorptive bisphosphonate. Furthermore, the new finding suggests an extended and hitherto-undescribed potential for clodronate in preventing the loosening of both implants and teeth, based on a dual beneficial effect: prevention of both bone resorption/osteolysis and of soft tissue/dental ligament destruction. Potential new therapeutic indications based on the collagenase-inhibiting effect of clodronate provide potential new therapeutic indications for a variety of diseased involving connective tissue breakdown, such as periodontal disease, arthritides, and tumor invasion.

Matrix metalloproteinase 13 (collagenase 3) in human rheumatoid synovium

OBJECTIVE

To show the eventual presence and extent of production of matrix metalloproteinase 13 (MMP-13, or collagenase 3) in rheumatoid synovial tissue samples and extracts, and to assess the inhibition characteristics of recombinant MMP-13.

METHODS

Immunohistochemical avidin-biotin-peroxidase complex staining/morphometry was used to analyze MMP-13-positive cells in situ. Neutral salt extraction of synovial tissue, electrophoresis of the extract in different buffer systems, and Western blotting were also used. The inhibitory properties of doxycycline, clodronate, pamidronate, and D-penicillamine for recombinant enzyme were determined with a soluble type II collagen assay.

RESULTS

MMP-13 was detected in fibroblast- and macrophage-like mononuclear cells in the synovial lining and stroma and in vascular endothelial cells. The overall expression of MMP-13 in these cells in the synovial stroma was high in rheumatoid arthritis (86 +/- 12%) compared with osteoarthritis (17 +/- 5%) patient samples (P = 0.0027). In a high-pH native electrophoresis gel, immunoreactivity to anti-MMP-1 and anti-MMP-13 were clearly separated, with anti-MMP-13-immunoreactive material migrating faster than anti-MMP-1-immunoreactive material. Finally, in contrast to MMP-1 and MMP-8, MMP-13 was found to be relatively resistant to the inhibitory effects of doxycycline and clodronate in vitro.

CONCLUSION

Due to its localization in synovial tissue, its substrate profile, increased expression, and relative resistance to known MMP inhibitors, MMP-13 is suggested to play a major role in the pathogenesis of tissue destruction in rheumatoid arthritis.

Diethyldithiocarbamate and nitric oxide synergize with oxidants and with membrane-damaging agents to injure mammalian cells

The effect of diethyldithiocarbamate (DDC) and sodium nitroprusside (SNP) on the killing of endothelial cells and on the release of arachidonate by mixtures of oxidants and membrane-damaging agents was studied in a tissue culture model employing bovine aortic endothelial cells labeled either with 51Chromium or 3arachidonic acid. While exposure to low, subtoxic concentrations of oxidants (reagent H2O2, glucose-oxidase generated peroxide, xanthine xanthine oxidase, AAPH-generated peroxyl radical, menadione-generated oxidants) did not result either in cell death or in the loss of membrane-associated arachidonic acid, the addition of subtoxic amounts of a variety of membrane-damaging agents (streptolysin S, PLA2, histone, taurocholate, wheatgerm agglutinin) resulted in a synergistic cell death. However, no significant amounts of arachidonate were released unless proteinases were also present. The addition to these reaction mixtures of subtoxic amounts of DDC (an SOD inhibitor and a copper chelator) not only very markedly enhanced cell death but also resulted in the release of large amounts of arachidonate (in the complete absence of added proteinases). Furthermore, the inclusion in DDC-containing reaction mixtures of subtoxic amounts of SNP, a generator of NO, further enhanced, in a synergistic manner, both cell killing and the release of arachidonate. Cell killing and the release of arachidonate induced by the DDC and SNP-containing mixtures of agonists were strongly inhibited by catalase, glutathione, N-acetyl cysteine, vitamin A, and by a nonpenetrating PLA2 inhibitor as well as by tetracyclines. A partial inhibition of cell killing was also obtained by 1,10-phenanthroline and by antimycin. It is suggested that DDC might amplify cell damage by forming intracellular, loosely-bound complexes with copper and probably also by depleting antioxidant thiols. It is also suggested that "cocktails" containing oxidants, membrane-damaging agents, DDC, and SNP might be beneficial for killing of tumor cells in vivo and for the assessment of the toxicity of xenobiotics in vitro.