Minocycline reduces gingival collagenolytic activity during diabetes. Preliminary observations and a proposed new mechanism of action

Bone cells and matrix bind chemically modified non-antimicrobial tetracycline

3H-labeled chemically modified, non-antimicrobial tetracycline (4-de-dimethyl-aminotetracycline; CMT) was injected intraperitoneally into neonatal rats and the animals killed at 20 min, 2 or 4 h after isotope injection. The binding of 3H-CMT in the calvariae was localized by light and electron microscopic autoradiography. At 20 min after injection, a high level of bound 3H-CMT was localized in the cells of the periosteum including the osteoblasts and preosteoblasts. The newly formed bone matrix was also heavily labeled by silver grains. At the ultrastructural level, many silver grains appeared over the cytoplasm of osteoblasts and preosteoblasts, particularly along the plasma membranes, in the periosteum. At 2 and/or 4 h after isotope injection, the number of silver grains over the cells was markedly reduced by that over the bone matrix appeared unchanged. These results indicate that, in addition to the mineral phase of bone, CMT directly binds to (or is taken up by) osteogenic cells and is then rapidly metabolized by these cells.

Positive influence of tetracycline on human fetal kidney in serum-free organ culture

Human fetal kidney explants can be maintained during 5 days in Leibovitz's L15, a basic serum-free medium. Because culture conditions are minimal for growth and differentiation, DNA synthesis drastically decreases during the first 48 h, but stabilizes thereafter. The addition of insulin plus transferrin significantly restores this important cellular function in kidneys of fetuses younger than 16 wk. However, renal explants from older fetuses are more difficult to culture: they respond less to growth factors and are more prone to necrosis. The objective of this study was to verify the influence of tetracycline, an antibiotic with anti-collagenase potential, on cultured kidney explants aged 17 to 20 wk. The addition of 20 micrograms/ml tetracycline did not influence DNA synthesis nor the effectiveness of insulin plus transferrin on cell proliferation. Nor did it change the activities of alkaline phosphatase and gamma-glutamyltransferase, two enzymic markers of brush border differentiation. After 5 days in L15 alone, explants often showed necrosis and an important reduction in both weight and volume. Insulin plus transferrin significantly restored these parameters to control values observed at Day 0, but evidence of necrosis was still present. Tetracycline alone markedly reduced explant necrosis resulting in a significant increase in weight and volume. The effectiveness of insulin plus transferrin on explant morphometry was not improved when tetracycline was added as third factor. These results indicate that insulin plus transferrin restores explant mass through cell proliferation, whereas tetracycline does so possibly through a reduction in extracellular matrix degradation. The two effects are not additive in cultured mid-term fetal kidneys.

Treating periodontal diseases by blocking tissue-destructive enzymes

A new therapeutic approach involves the discovery by the "Stony Brook group," that tetracyclines, but not other antibiotics, can inhibit host-derived collagen-destructive enzymes. This newly discovered property of tetracyclines is unrelated to the antimicrobial activity of these drugs. Examples support the hypothesis that this unexpected property of tetracyclines provides a new approach to treating periodontal diseases as well as a variety of medical disorders.

In vivo modulation of several anticancer agents by beta-carotene

The ability of the collagenase inhibitor minocycline and of beta-carotene to act as positive modulators of cytotoxic anticancer agents was assessed in vitro and in vivo. Cell-culture studies were conducted using the human SCC-25 squamous carcinoma cell line. Simultaneous exposure of the cells to minocycline and beta-carotene or 13-cis-retinoic acid along with cisplatin (CDDP) resulted in a small decrease in the cytotoxicity of the CDDP. The addition of each of the modulator combinations for 1 h or 24 h to treatment with melphalan (L-PAM) or carmustine (BCNU) resulted in greater-than-additive cytotoxicity with each of four regimens. The modulator combinations of minocycline and beta-carotene applied for 1 h or 24 h and the modulator combination of minocycline and 13-cis-retinoic acid produced greater-than-additive cytotoxicity at 50 microM 4-hydroperoxycyclophosphamide (4-HC), whereas minocycline and 13-cis-retinoic acid applied for 1 h was antagonistic with 4-HC and the other modulator treatments at low concentrations of 4-HC resulted in subadditive cytotoxicity. The effect of treatment with beta-carotene alone and in combination with several different anticancer agents was examined in two murine solid tumors, the FSaII fibrosarcoma and the SCC VII carcinoma. Administration of the modulators alone or in combination did not alter the growth of either tumor. Whereas increases in tumor growth delay occurred with the antitumor alkylating agents and beta-carotene and with minocycline and beta-carotene, a diminution in tumor growth delay was produced by 5-fluorouracil in the presence of these modulators. The modulator combination also resulted in increased tumor growth delay with adriamycin and etoposide. Tumor-cell survival assay showed increased killing of FSaII tumor cells with the modulator combination and melphalan or cyclophosphamide as compared with the drugs alone. These results indicate that further investigation of this modulator strategy is warranted.

Captopril inhibits the 72 kDa and 92 kDa matrix metalloproteinases

Gelatinases are metalloproteinases in the kidney which can cleave type IV collagen as well as gelatin. We partially purified the 72 kDa and 92 kDa gelatinases. The gelatinolytic activity was measured by zymography and a quantitative biotin-avidin assay. By zymography, captopril in concentrations of 20 mM and 40 mM added to the incubation buffer reduced the gelatinolytic activity in a dose-dependent manner. The addition of zinc in a concentration of 50 to 100 microM reversed most of the inhibitory effect of captopril. By the biotin-avidin assay, captopril in a concentration of 30 to 50 nM reduced half of either the 72 kDa or 92 kDa gelatinolytic activity. Zinc in a concentration of 50 microM completely reversed the inhibitory effect of 1 microM captopril on both gelatinases. Lisinopril, a non-sulfhydryl ACE inhibitor, similarly inhibited the gelatinases, but a 100-fold higher concentration of the drug was needed. These findings suggest that captopril reversibly inhibits the 72 kDa and 92 kDa metalloproteinases by interacting with the zinc ion at their active sites. This inhibitory effect is observed with captopril levels comparable to the concentrations needed to inhibit the angiotensin converting enzyme in vivo and may at least partially explain some of the renoprotective effects seen with this drug.

Reactive oxygen species activate and tetracyclines inhibit rat osteoblast collagenase

Recent studies have demonstrated that tetracyclines (TCs) scavenge reactive oxygen species (ROS). Hypochlorous acid (HOCl), an ROS produced by neutrophils, has been shown to activate neutrophil procollagenase. The objective of the present study was to determine whether (1) HOCl also activated osteoblast procollagenase and (2) TCs inhibited this enzyme in the presence of HOCl. HOCl (5 microM) activated the proenzyme approximately sixfold (P < 0.01) from the medium of PTH-treated UMR-106-01 osteoblastic osteosarcoma cells as determined by functional collagenase assay (3H-methyl-labeled collagen substrate). Doxycycline (50-400 microM) and chemically modified tetracycline, CMT-1 (100-400 microM), significantly inhibited collagenase activity 50-90% and 40-80%, respectively, in the presence of 5 microM HOCl. Concentrations of 6-25 microM doxycycline and 10-50 microM CMT-1 had no significant effect. Furthermore, an excess concentration of cation (50 mM CaCl2 or 50 microM ZnCl2) added to the incubation mixtures containing either doxycycline or CMT-1 did not restore collagenase activity, as demonstrated by SDS-PAGE-fluorography. These data suggested that TCs reduced available HOCl and thus prevented the hypochlorous acid conversion of the osteoblast proenzyme to active collagenase. TCs may have therapeutic potential in the treatment of periodontitis and other diseases by several mechanisms that inhibit pathologic collagen breakdown.

Effect of tetracyclines which have metalloproteinase inhibitory capacity on basal and heparin-stimulated bone resorption by chick osteoclasts

Several tetracyclines (TETs) are potent inhibitors of collagenase (CGase) and can inhibit connective tissue degradation in a variety of inflammatory and degenerative disorders. The role of CGase in bone resorption by osteoclasts (OC) remains unclear. Disaggregated OCs from chick embryos were cultured for 24 h on devitalized bovine cortical bone +/- heparin in the presence of various TETs. Doxycycline (Dox) inhibited pit formation in a dose-dependent manner. CMT, a TET derivative which inhibits matrix metalloproteinases (MMPs) but is not antimicrobial, also inhibited chick OC bone resorption. Heparin markedly stimulated bone resorption at 5 micrograms/ml, which was reversed by Dox, 5 micrograms/ml. TETs can reversibly inhibit both basal and heparin-stimulated bone resorption by chick OCs. These findings suggest that MMPs may play a role in osteoclastic bone resorption, and that safe and effective inhibitors of MMPs, including certain TETs, might have a potential therapeutic role.

Inhibition of epithelial cell matrix metalloproteinases by tetracyclines

The effects of tetracyclines on periodontal epithelial cells were investigated by culturing cells from porcine rests of Malassez in the presence of oxytetracycline, doxycycline or one of two analogues of tetracycline bearing no antimicrobial activity. Matrix metalloproteinase activity produced by the epithelial cells was assayed by quantitation of radioactive gelatin degradation and by gelatin enzymography. The results show that all tested tetracyclines exerted a direct dose-dependent inhibitory effect on epithelial cell gelatinases. Furthermore, epithelial cells cultured with doxycycline, oxytetracycline and de-dimethylaminotetracycline in concentrations ranging from 1 to 50 micrograms/ml showed a marked reduction in secreted gelatinase activity when grown in alpha minimum essential medium in the absence of fetal calf serum. Viability of cells following this treatment, measured as lactate dehydrogenase activity released to the cell media, was not affected by the presence of any of these drugs at the concentrations used. Scanning electron microscopy revealed striking morphologic changes of the cells following treatment with tetracyclines in the absence of serum which include rounding, decreased intracellular contacts and increased intercellular spaces. No such effects were seen in cells cultured in the presence of serum. These results provide evidence that periodontal epithelial cells produce matrix metalloproteinases whose activities are inhibited by tetracyclines and their non-antimicrobial analogues at concentrations present in gingival crevicular fluid following tetracycline therapy. When used as adjuncts in periodontal therapy, tetracyclines may therefore inhibit epithelial cell mediated degradation of basement membrane and subepithelial connective tissue.

Tetracycline and doxycycline inhibit pleural fluid metalloproteinases. A possible mechanism for chemical pleurodesis

We hypothesized that inhibition of matrix-degrading metalloproteinases (MMPs) accounts for a portion of the pleural fibrosis and adhesions of tetracycline pleurodesis. MMPs recently have been described in pleural fluid from patients with both exudative and transudative effusions. Since tetracyclines are recognized inhibitors of other metalloproteinases, we investigated their inhibitory capacity in pleural fluid. High concentrations of several different tetracyclines reduced MMP activity of pleural fluid by more than 75 percent. Lower concentrations (< or = 1 mg/ml) had only modest inhibitory effects. High concentration of of tetracyclines also inhibited cell synthesis of MMPs, in vitro, but other measures of vital cell function were also impaired. We conclude that tetracyclines are effective inhibitors of MMP activity in pleural fluid and may also reduce synthesis of MMPs via non specific cell injury. These data suggest a possible mechanism to account for tetracycline pleurodesis; ie, an inhibition of MMP activity in pleural fluid.

Reduction of proteolytic degradation by chlorhexidine

The present investigation was designed to evaluate the effect of the antimicrobial agent chlorhexidine on proteolytic degradation. Chlorhexidine, at a final concentration of 0.01%, significantly (p = 0.05) affected the degradation of the general chromogenic substrate azocoll by both commercial proteases and cell-bound bacterial proteases. Reduction of proteolytic degradation was observed following pre-treatment of either azocoll or bacterial cells with chlorhexidine. Chlorhexidine was also found to prevent degradation of type I collagen by Porphyromonas gingivalis cells. The mechanism of inhibition of proteolytic degradation appears to be related to an electrostatic chlorhexidine-protein interaction.

Reflex sympathetic dystrophy: occurrence of chronic edema and nonimmune bullous skin lesions

BACKGROUND

Reflex sympathetic dystrophy (RSD) is a poorly understood syndrome of post-traumatic pain, autonomic dysfunction, and progressive tissue atrophy. Classical descriptions of the cutaneous manifestations of RSD are usually limited to skin atrophy, vascular instability, and hyperhidrosis.

OBJECTIVE

Our objective was to further delineate the cutaneous changes in RSD.

METHODS

We have observed RSD-related inflammatory and bullous lesions in nine patients with active RSD.

RESULTS

Eight patients had significant edema of involved skin, two patients had evidence of a pigmented purpura-like inflammatory dermatitis, and two other patients had bullae on involved skin. Ultrastructural studies on a biopsy specimen from one patient with recurrent bullae revealed a disrupted basement membrane and abnormal anchoring fibrils.

CONCLUSION

Skin disease in RSD is more diverse than commonly appreciated and includes severe edema, inflammatory lesions, and a nonimmune bullous eruption.

Matrix metalloproteinases: a review

Matrix metalloproteinases (MMPs) are a family of nine or more highly homologous Zn(++)-endopeptidases that collectively cleave most if not all of the constituents of the extracellular matrix. The present review discusses in detail the primary structures and the overlapping yet distinct substrate specificities of MMPs as well as the mode of activation of the unique MMP precursors. The regulation of MMP activity at the transcriptional level and at the extracellular level (precursor activation, inhibition of activated, mature enzymes) is also discussed. A final segment of the review details the current knowledge of the involvement of MMP in specific developmental or pathological conditions, including human periodontal diseases.

beta-cyclodextrin tetradecasulfate/tetrahydrocortisol +/- minocycline as modulators of cancer therapies in vitro and in vivo against primary and metastatic Lewis lung carcinoma

Tetrahydrocortisol, beta-cyclodextrin tetradecasulfate, and minocycline used alone or in combination are not very cytotoxic toward EMT-6 mouse mammary tumor cells growing in monolayer. Tetrahydrocortisol (100 microM, 24 h) and beta-cyclodextrin tetradecasulfate (100 microM, 24 h) protected EMT-6 cells from the cytotoxicity of CDDP, melphalan, 4-hydroperoxycyclophosphamide, BCNU, and X-rays under various conditions of oxygenation and pH. Minocycline (100 microM, 24 h) either had no effect upon or was additive with the antitumor alkylating agents or X-rays in cytotoxic activity toward the EMT-6 cells in culture. The combination of the three modulators either had no effect upon or was to a small degree protective against the cytotoxicity of the antitumor alkylating agents or X-rays. The Lewis lung carcinoma was chosen for primary tumor growth-delay studies and tumor lung-metastases studied. Tetrahydrocortisol and beta-cyclodextrin tetradecasulfate were given in a 1:1 molar ratio by continuous infusion over 14 days, and minocycline was given i.p. over 14 days, from day 4 to day 18 post tumor implantation. The combination of tetrahydrocortisol/beta-cyclodextrin tetradecasulfate diminished the tumor growth delay induced by CDDP and melphalan and produced modest increases in the tumor growth delay produced by cyclophosphamide and radiation. Minocycline co-treatment increased the tumor growth delay produced by CDDP, melphalan, radiation, bleomycin, and, especially cyclophosphamide, where 4 of 12 animals receiving minocycline (14 x 5 mg/kg, days 4-18) and cyclophosphamide (3 x 150 mg/kg, days 7, 9, 11) were long-term survivors. The 3 modulators given in combination produced further increases in tumor growth delay with all of the cytotoxic therapies, and 5 of 12 of the animals treated with the 3-modulator combination and cyclophosphamide were long-term survivors. Although neither tetrahydrocortisol/beta-cyclodextrin tetradecasulfate, minocycline, nor the three modulator combination impacted the number of lung metastases, there was a decrease in the number of large lung metastases. Treatment with the cytotoxic therapies alone reduced the number of lung metastases. Addition of the modulators to treatment with the cytotoxic therapies resulted in a further reduction in the number of lung metastases. These results indicate that agents that inhibit the breakdown of the extracellular matrix can be useful additions to the treatment of solid tumors.

Periodontopathic potential of two strains of Porphyromonas gingivalis in gnotobiotic rats

Germ-free rats were monoinfected with Porphyromonas gingivalis strains 381 or A7A1-28 for 42 or 84 days. Both strains induced substantial destruction of alveolar bone and soft tissue when compared to non-infected controls, but the patterns were different. Strain A7A1-28 was associated with increased activity of host collagenase and gelatinase at 42 days, whereas the activity was elevated to a lesser extent at 84 days. Strain 381 showed a moderate increase in host proteinase activity at 42 days, and this remained unchanged until day 84. Strain A7A1-28 was associated with more bone loss than strain 381 by a morphometric analysis that detects horizontal bone loss in the maxilla. Strain 381 was associated with more bone loss than strain A7A1-28 by a radiographic method that detects vertical intrabony defects in the mandible. Infection with one strain gave rise to serum and salivary antibodies strongly reactive to the infecting strain and moderately reactive to antigens from the other strain. This indicates that some antigenic similarity exists between the strains and that there are also strain or perhaps serotype differences in antibody responses induced by infection. Thus two strains of P. gingivalis differing in antigenicity and pathogenicity in the mouse model of the subcutaneous abscess cause substantial periodontal destruction in the germ-free rat. The disease pattern is, however, different, with strain A7A1-28 inducing mostly horizontal bone loss and strain 381 mostly vertical.

Tetracycline administration increases protein (presumably procollagen) synthesis and secretion in periodontal ligament fibroblasts of streptozotocin-induced diabetic rats

Streptozotocin-induced, insulin-deficient diabetic adult rats were daily administrated either minocycline or a chemically-modified non-antimicrobial tetracycline (CMT) by oral gavage for a 3-week time period; untreated diabetic and non-diabetic rats served as controls. On day 21, all rats received an intravenous injection of 3H-proline followed by perfusion fixation with an aldehyde mixture at 20 minutes and 4 hours after isotope injection. The upper and lower mandibles of these rats were dissected and processed for quantitative electron microscopic autoradiography to study 3H-proline utilization by fibroblasts in the periodontal ligament (PDL) of molars. In the non-diabetic controls, at 20 min after 3H-proline injection, radioprecursor was incorporated by the Golgi-RER system of PDL fibroblasts. At the 4-h time period, most of the label was present over the collagen fibers around these cells. In contrast, PDL fibroblasts in the untreated diabetic rats showed marked abnormalities ultrastructurally and minimal uptake (20 min) and secretion (4 h) of labeled proline. At both time periods, in both minocycline- and CMT-treated diabetic rats, fibroblasts were structurally more normal and the radioprecursor was localized in the fibroblasts and the PDL matrix in a pattern similar to that seen in the control rats. These results suggest that the diabetes-induced structural abnormalities and suppression of synthesis and secretion of protein (presumably collagen and its precursor) by PDL fibroblasts can be restored to near-normal by administration of a tetracycline and that this effect is mediated by a non-antimicrobial property of this family of antibiotics.

Tetracyclines inhibit intracellular muscle proteolysis in vitro

Tetracycline antibiotics (TETs) have a recently discovered novel action: inhibition of extracellular metalloproteinase activity, especially that of collagenase and gelatinase. This property, now confirmed in 8 different laboratories using > 40 tissue sources, includes natural and semi-synthetic TETs as well as a chemically modified TET (CMT) devoid of antimicrobial activity. We have used 14C-Tyr biosynthetically labelled intracellular proteins in L-6 myoblast culture as a test system to assess intracellular proteolysis. Starvation accelerates proteolysis, which can be suppressed by agents such as insulin or serum. Minocycline, doxycycline, and CMT all retarded the rate of intracellular protein degradation in a dose dependent manner. These agents also demonstrated marked synergism with insulin. A CMT derivative (pyrazole) stripped of one of its metal chelation sites and lacking anti-collagenase activity, also lost its antiproteolytic effect. CMT at physiologic concentrations (< or = 5 micrograms/ml) had no effect on protein synthesis, but at 15 micrograms/ml (pharmacologic), a suppressive effect was noted. These findings demonstrate that TETs can inhibit protein degradation as well as synthesis in a mammalian muscle-derived cell line.

Recent advances in periodontal diagnosis and treatment: exploring new treatment alternatives

A better understanding of the etiology and pathogenesis of periodontal diseases provides clinicians and researchers with a number of new diagnostic techniques and treatment alternatives. These new developments may also offer the clinician additional information for treatment planning.

Reduction of the severity of canine osteoarthritis by prophylactic treatment with oral doxycycline

OBJECTIVE

In vitro studies have indicated that levels of neutral metalloproteinases in osteoarthritic (OA) cartilage are elevated and that doxycycline (doxy) inhibits collagenolytic and gelatinolytic activity in extracts of OA cartilage. The purpose of the present study was to test the effect of oral doxy administration on the severity of cartilage degeneration in OA.

METHODS

OA was induced in 12 adult mongrel dogs by transection of the anterior cruciate ligament (ACL) 2 weeks after dorsal root ganglionectomy. Six dogs received doxy orally from the day after ACL transection until they were killed 8 weeks later; the other 6 served as untreated OA controls.

RESULTS

The unstable knee of each untreated dog exhibited extensive full-thickness cartilage ulceration of the medial femoral condyle. In sharp contrast, cartilage on the distal aspect of the femoral condyle of the unstable knee was grossly normal in 2 doxy-treated dogs, and exhibited only thinning and/or surface irregularity in the others. Degenerative cartilage lesions on the medial trochlear ridge, superficial fibrillation of the medial tibial plateau, and osteophytosis were, however, unaffected by doxy treatment. Collagenolytic activity and gelatinolytic activity in cartilage extracts from OA knees of untreated dogs were 5-fold and 4-fold greater, respectively, than in extracts from dogs given doxy.

CONCLUSION

Prophylactic administration of doxy markedly reduced the severity of OA in weight-bearing regions of the medial femoral condyle. It remains to be determined whether administration of doxy after OA changes have developed is also effective.

Inhibition of enzymatic activity of phospholipases A2 by minocycline and doxycycline

Extracellular phospholipases A2 play an important role in articular and extra-articular inflammatory processes. Secretory non-pancreatic phospholipase A2 (PLA2) has been implicated in the pathogenesis of articular inflammation in rheumatoid arthritis, whereas pancreatic PLA2 contributes to the tissue damage associated with acute pancreatitis. Since in experimental models lipophilic tetracyclines such as minocycline and doxycycline are antiinflammatory, we examined their effects on PLA2 activity using two assay systems in vitro. We found that minocycline and to a lesser degree doxycycline were markedly inhibitory to both pancreatic and non-pancreatic PLA2. Using [14C]oleic acid labeled Escherichia coli membrane phospholipids as substrate, the IC50 values for minocycline and doxycycline were 3.6 x 10(-5) M (18 micrograms/mL) and 0.98 x 10(-4) M (47 micrograms/mL), respectively. In a scooting mode assay using the synthetic phospholipid 1-palmitoyl-2-(10-pyrenedecanoyl)-3-L-phosphatidylmethanol as substrate, IC50 values for minocycline were 5 microM (2.47 micrograms/mL) for non-pancreatic PLA2 and 8 microM (3.95 micrograms/mL) for pancreatic PLA2. Addition of excess calcium up to 50 mM did not reverse the inhibitory activity of tetracyclines. We conclude that lipophilic tetracyclines inhibit PLA2, probably by interaction with the substrate, and may be a useful adjunct in the therapy of inflammatory conditions in which PLA2 is implicated pathogenetically.

Minocycline in combination with chemotherapy or radiation therapy in vitro and in vivo

In the present study the potential of minocycline, a semisynthetic tetracycline that inhibits collagenase activity in vivo, as an adjuvant to standard anticancer therapies was explored in vitro and in vivo. In EMT-6 cells, minocycline proved to be only minimally cytotoxic, producing a 50% cell kill at concentrations of 132 and 220 microM in normally oxygenated and hypoxic cells, respectively, after 24 h exposure to the drug. In vitro, there appeared to be no interaction between minocycline and cisplatin (CDDP), melphalan, 4-hydroperoxycyclophosphamide, or radiation. In tumor-cell survival studies using the FSaIIC murine fibrosarcoma, short-term treatment with minocycline (5 x 5 mg/kg given over 24 h) was only minimally cytotoxic and did not alter the tumor response to a range of radiation doses. However, when minocycline (5 x 5 mg/kg given over 24 h) was added to treatment with cyclophosphamide, there was a 4-fold increase in FSaIIC tumor-cell killing across the dose range of cyclophosphamide doses tested, whereas the killing of bone marrow granulocyte macrophage colony-forming units (CFU-GM) remained unchanged. The Lewis lung carcinoma was used to assess the response of both the primary tumor and metastatic lung disease to treatment with minocycline (14 x 5 mg/kg) given alone or in combination with several cytotoxic anticancer drugs or with radiation delivered locally to the primary tumor. Of the various therapies tested, minocycline proved to be especially effective as an addition to treatment with cyclophosphamide both in increasing the response of the primary tumor and in reducing the number of lung metastases. The tumor growth delay produced by melphalan, radiation, Adriamycin, and bleomycin was also increased by the addition of minocycline to these therapies. These results indicate that minocycline given in clinically achievable doses may be an effective addition to some standard therapeutic regimens and that the mechanism of modulation by minocycline is likely to involve an effect of the drug on the host and not its direct interaction with other therapeutic modalities at the level of the tumor cell.

Implications of diabetes mellitus and periodontal disease

The dental profession is acutely aware of oral health problems associated with diabetes mellitus and clinical manifestations indicative of occult forms of the disease. Periodontal disease is common in patients with diabetes, and its effective management in diabetic patients requires cooperation involving the patient, physician, diabetes educator, dentist, and other allied health care providers. While these patients categorically appear more prone to diseases affecting the supporting tissues of the teeth, preservation of functional dental integrity can be attained by effective control of contributing systemic and local factors. This paper will discuss periodontal disease, its relationship to diabetes, proposed mechanisms of interaction, and management of periodontal disease in the diabetic patient.

Immunization with Porphyromonas (Bacteroides) gingivalis fimbriae protects against periodontal destruction

Adhesive fimbriae from Porphyromonas gingivalis are cell surface structures which may be important in the virulence of this oral pathogen and thus may serve as a critical or target antigen. Immunization with highly purified 43-kDa fimbrial protein protected against periodontal tissue destruction when tested in the P. gingivalis-infected gnotobiotic rat model. A similarly highly purified 75-kDa cell surface component did not provide protection. Heat-killed whole-cell and sonicated cell surface extracts which contain the 43-kDa protein as well as the 75-kDa component were protective also. This study indicates that the fimbrial protein may serve as a model for the development of effective vaccines against periodontitis, a major human oral disease.

Tetracycline administration increases collagen synthesis in osteoblasts of streptozotocin-induced diabetic rats: a quantitative autoradiographic study

Streptozotocin-induced, insulin-deficient diabetic rats were administrated either minocycline (MC) or a chemically modified non-antimicrobial tetracycline (CMT) by oral gavage for a 3-week period; untreated diabetic and nondiabetic rats served as controls. On day 21, all rats received an intravenous injection of 3H-proline followed by perfusion fixation with an aldehyde mixture at 20 minutes and 4 hours after isotope injection. The parietal bones of these rats were dissected and processed for quantitative electron microscopic autoradiography to study 3H-proline utilization by osteoblasts. At 20 minutes after 3H-proline injection, radioprecursor was incorporated by the Golgi-RER system of the osteoblasts in the periosteal surface of the control rats. At the 4-hour time period, most of the label was present over the collagen fibers of the osteoid. In contrast, the flattened bone-lining cells in the untreated diabetic rats showed minimal uptake (20 minutes) and secretion (4 hours) of labeled proline. In both MC and CMT-treated diabetic rats, the radioprecursor was localized in the osteoblasts and osteoid matrix in a pattern similar to that seen in the control rats at both 20 minutes and 4 hours after isotope injection. Labeling of the osteoid by the radioprecursor was greater as a result of CMT treatment than during minocycline treatment. These results suggest that the diabetes-induced suppression of synthesis and secretion of protein (presumably collagen and its precursor) by osteoblasts can be restored to near-normal levels by administration of tetracycline(s) and that this effect is mediated by a non-antimicrobial property of these antibiotics.

HPLC determination of a chemically modified nonantimicrobial tetracycline: biological implications

Chemically modified tetracycline (4-de-dimethylamino tetracycline), like commercially available tetracyclines, is known to inhibit experimentally induced pathologic collagen breakdown. A method for measurement of chemically modified tetracycline in small volumes (50 microliters) of rat serum was developed using reversed-phase HPLC; this was necessary because this tetracycline analog lacks antimicrobial activity and, therefore, cannot be measured with standard bioassays. This method uses the same solution for extraction and elution thus providing a simple and rapid assay for both drugs. Using this technique, the concentration of chemically modified tetracycline and tetracycline were determined in rat serum at different times after oral administration. The serum concentration of chemically modified tetracycline was much higher than that for tetracycline, and its serum half-life was greater. The IC50 of chemically modified tetracycline and tetracycline, as inhibitors of collagenase from rat polymorphonuclear leukocytes, was determined and found to be 4.1 x 10(-8) M (0.02 micrograms/ml) and 2.4 x 10(-4) M (120 micrograms/ml), respectively. Based on the serum levels of these drugs after oral administration, and their IC50 values, chemically modified tetracycline is potentially a far more potent inhibitor of excess collagenase activity than tetracycline, during pathologic conditions, and may have the added advantage of not producing some of the typical complications of long-term antibiotic therapy.

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

The concentrations of doxycycline and 4-de-dimethylaminotetracycline required to inhibit 50% of collagenase activity were found to be 15 to 30 microM for human neutrophil and gingival crevicular fluid collagenases. Fibroblast collagenase was relatively resistant to inhibition by tetracyclines; the 50% inhibitory concentrations of doxycycline and 4-de-dimethylaminotetracycline were 280 and 510 microM, respectively.

Collagenase activity in recurrent periodontitis: relationship to disease progression and doxycycline therapy

Previous reports have suggested that active progression of periodontitis may be correlated with increased collagenolytic activity, and that improved clinical conditions after tetracycline treatment may be explained by inhibition of host collagenase. Eighty-two patients with a recent history of periodontal abscesses and/or loss of gingival attachment level (GAL) despite active periodontal therapy were enrolled in a double-blind, randomized, placebo-controlled trial. Clinical measurements, sampling of gingival crevicular fluid (GCF) and subgingival scaling were performed every 2 months. If any site exhibited greater than 2 mm loss of GAL or a periodontal abscess, patients were administered either 100 mg doxycycline per day for 3 weeks or placebo. During 12 months of monitoring, 55 patients exhibited recurrent active disease and were then randomly assigned to either the doxycycline (n = 30) or placebo (n = 25) groups. Analysis of active collagenase and latent collagenase in GCF samples were determined by functional assays and quantitated after SDS-PAGE and fluorography. Collagenase activities were assayed at sites exhibiting active destruction (study site), at sites with pocket depth comparable to the study site but without active destruction, and at healthy sites. Clinical measurements of GAL and collagenase activity were made at intervals between 1 wk and 7 months after completion of the drug regime. Within 7 months, 15 out of 19 patients on placebo exhibited recurrent disease compared to 13 out of 29 patients on doxycycline. Collagenase activity exhibited large variations among patients and was analyzed as presence or absence of active collagenase with a logistic model.(ABSTRACT TRUNCATED AT 250 WORDS)

The tetracyclines in dermatology

Tetracycline is one of the most widely used antibiotics. It may share some properties with conventional immunosuppressive drugs and act as an anti-inflammatory agent in the treatment of inflammatory disease. This article reviews cutaneous diseases that have been treated with tetracyclines and their antiinflammatory and immunosuppressive properties.

Tetracycline administration restores osteoblast structure and function during experimental diabetes

Osteopenia is a recognized complication of diabetes mellitus in humans and experimental animals. We recently found that tetracyclines prevent osteopenia in the streptozotocin-induced diabetic rat and that this effect was associated with a restoration of defective osteoblast morphology (Golub et al., 1990). The present study extends these initial ultrastructural observations by assessing osteoblast function in the untreated and tetracycline-treated diabetic rats. After a 3-week protocol, non-diabetic control and diabetic rats, including those orally administered a tetracycline, minocycline (MC), or a non-antimicrobial tetracycline analog (CMT), were perfusion-fixed with an aldehyde mixture; the humeri were dissected and processed for ultracytochemical localization of alkaline phosphatase (ALPase) and Ca-ATPase activities. Some rats from each experimental group received an intravenous injection of 3H-proline as a radioprecursor of procollagen, and the humeri were processed for light microscopic autoradiography. In addition, the osteoid volume in each experimental group was quantitatively examined by morphometric analysis of electron micrographs. During the diabetic state, active cuboidal osteoblasts in the endosteum of control rats were replaced by flattened bone-lining cells that contained few cytoplasmic organelles for protein synthesis (Golgi-RER system), and active transport (mitochondria). Treating diabetic rats with MC, and even more so with CMT, appeared to "restore" osteoblast structure. During diabetes, bone-lining cells incorporated little 3H-proline or secreted little labeled protein and produced only a very thin osteoid layer. Tetracycline administration to the diabetics increased both the incorporation of 3H-proline by osteoblasts and their secretion of labeled protein toward the osteoid matrix, in a pattern similar to that seen in the non-diabetic controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Periodontal bone level and gingival proteinase activity in gnotobiotic rats immunized with Bacteroides gingivalis

Bacteroides gingivalis is associated with various forms of periodontal disease. To assess the role of the immune response in modulating B. gingivalis-associated periodontal disease, the effect of immunization of B. gingivalis-induced periodontal bone loss was evaluated in gnotobiotic rats. Male Sprague-Dawley rats immunized with various doses of whole cells or sham-immunized with incomplete Freund's adjuvant were monoinfected with B. gingivalis in carboxymethylcellulose by gavage. Two additional groups served as either sham-immunized or untreated germ-free controls. Forty-two days after infection, all rats were killed, periodontal bone level was assessed morphometrically and radiographically, and gingival proteinase (mammalian collagenase and acid cathepsin) activity was assessed biochemically. B. gingivalis was present in oral samples from all monoinfected rats, and no contaminating bacteria were detected in any oral or fecal sample. Animals immunized with B. gingivalis cells had elevated serum and saliva antibodies to whole cells and partially purified fimbriae from B. gingivalis. Infected sham-immunized rats had significantly more periodontal bone loss than noninfected controls, whereas the periodontal bone level in infected rats immunized with 10(10) B. gingivalis cells was similar to that of the noninfected controls. The activities of gingival collagenase and cathepsin B and L were high in sham-immunized infected rats and low in all other animal groups. In conclusion, it is possible to reduce B. gingivalis-induced periodontal tissue loss in gnotobiotic rats by immunization.

Tetracyclines inhibit connective tissue breakdown: new therapeutic implications for an old family of drugs

Tetracyclines have long been considered useful adjuncts in peridontal therapy based on their antimicrobial efficacy against putative periodontopathogens. However, recently these drugs were found to inhibit mammalian collagenases and several other matrix metalloproteinases (MMPs) by a mechanism independent of their antimicrobial activity. Evidence is presented that this property may be therapeutically useful in retarding pathologic connective tissue breakdown, including bone resorption. The experiments leading to this discovery are described and possible mechanisms are addressed, including the specificity of tetracyclines' anti-collagenase activity, the role of the drugs' metal ion (Zn2+, Ca2+)-binding capacity, and the site on the tetracycline molecule responsible for this nonantimicrobial property. Of extreme interest, the tetracycline molecule has been chemically modified in multiple ways, generating a new family of compounds called CMTs (chemically modified tetracyclines) that lack antimicrobial but still retain anti-collagenase activity. The first of these CMTs, 4-de-di-methylaminotetracycline, was found not to produce a major side-effect of antimicrobial tetracycline therapy--its administration to experimental animals did not result in the emergence of tetracycline-resistant microorganisms in the oral flora and gut. Numerous examples of the clinical potential of this non-antimicrobial property of tetracyclines in the treatment of periodontal and several medical diseases (e.g., sterile corneal ulcers, rheumatoid arthritis, skin bullous lesions, tumor-induced angiogenesis and metastasis) are discussed.

Enhanced repair and regeneration of periodontal lesions in tetracycline-treated patients. Case reports

A group of cases is presented in which dramatic repair and regeneration of periodontal tissues lost as a result of periodontitis have occurred following systemic administration of tetracycline either alone or in combination with other forms of periodontal therapy. The nature and extent of regeneration demonstrated in these patients appears to be more dramatic than what has been shown previously when more conventional forms of periodontal therapy were utilized, even including bone grafting and guided tissue regeneration. The type of repair described has been shown in many instances to be long standing and is probably not totally related to the antibacterial characteristics of tetracycline. It is suggested that the ability of this drug to inhibit collagenolytic enzymes (collagenases) may have influenced the favorable clinical results achieved. The anti-collagenolytic properties of tetracycline are being considered with increasing frequency in the treatment of other systemic diseases characterized by collagen breakdown such as corneal ulcers, rheumatoid arthritis, diabetes, and dystrophic epidermolysis bullosa. Given the highly collagenous nature of the tissues of the periodontium, this report suggests that tetracycline could be of considerable value in the treatment of some types of periodontitis.

A randomized, placebo-controlled trial of doxycycline: effect on the microflora of recurrent periodontitis lesions in high risk patients

Twenty-seven patients with a recent history of periodontal abscesses and/or loss of gingival attachment level (GAL) despite active periodontal therapy were enrolled in a double-blind, randomized, placebo-controlled trial. Clinical measurements and subgingival scaling were performed every 2 months. When a site exhibited greater than or equal to 2 mm loss of GAL or a periodontal abscess, patients were administered either doxycycline at a dosage of 200 mg to start and 100 mg per day for 3 weeks, or a placebo. Clinical measurements of GAL and microbial analysis of subgingival plaque at study and control sites were made at the time of active disease and at intervals of 1 week and 7 months after completion of the drug regime. Plaque samples were screened for the presence of Actinobacillus actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Bacteroides intermedius (Bi), Eikenella corrodens (Ec) and Fusobacterium nucleatum (Fn) by indirect immunofluorescence antibody technique and for spirochetes (Sp) using Ryu's stain. Based on presence or absence analysis of the sum scores of the 6 pathogens, both the placebo (n = 10) and the doxycycline groups (n = 17) exhibited similar scores at the time of detection of active disease (mean placebo = 2.38 +/- 0.32; mean doxycycline = 2.95 +/- 0.27; P = 0.18). One week after treatment, the probability of detection was unchanged in the placebo group (mean placebo = 3.14 +/- 0.47), but was significantly reduced in the doxycycline group (mean doxycycline = 1.77 +/- 0.26; P = 0.0002). Study (active) sites exhibited scores 2 to 3 times higher than control (inactive) sites before doxycycline treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Doxycycline-tricalcium phosphate composite graft facilitates osseous healing in advanced periodontal furcation defects

The purpose of this study was to compare the effectiveness of a tricalcium phosphate, plaster of paris, and doxycycline composite graft to surgical debridement alone in the treatment of Class II and Class III furcation defects. Fifteen patients with adult periodontitis and at least two mandibular molars with Class II or III furcation defects were selected. A total of 40 sites were treated: 26 were Class II defects and 14 were Class III. Following initial therapy one site was randomly selected to receive the composite graft while the remaining site served as the surgically debrided control. Osseous healing was evaluated by direct measurements from an acrylic stent at the time of graft surgery and at the 6-month reentry. Following surgery each patient was placed on doxycycline 100mg/day for 10 days. The absence of clinical inflammation and infection during the healing process provided additional substantiation of the biocompatibility of the grafting materials. Results after 6 months indicated that sites treated with the composite graft had improved defect fill, defect resolution, probing depths, and clinical attachment levels when compared to the surgically debrided controls. Defect fill was 3.7 times greater in grafted sites and these sites were 4.0 times more likely to have 50% or greater defect fill. The effect of grafting was more pronounced in Class III defects where horizontal defect fill and gain of clinical attachment was achieved only in grafted sites. The plaster of paris functioned well as a binder, preventing particle scatter and facilitating graft retention. Additionally the plaster served as a vehicle to carry and retain the doxycycline at the treated site. These short-term results point to the potential of a composite graft containing tricalcium phosphate, plaster of paris, and doxycycline in promoting healing of furcation lesions.

Suppression of human neutrophil functions by tetracyclines

Tetracycline inhibition of neutrophil-associated collagenolysis has been the focus of a number of investigations. Evidence has suggested that this inhibition results from the ability of this family of antimicrobial drugs to bind divalent cations such as Ca2+ and Zn2+, two cations that are required for full expression of activity of metalloproteinases such as collagenase and gelatinase. Data presented in this study demonstrate that tetracyclines can also inhibit neutrophil-mediated RBC lysis, superoxide anion synthesis, degranulation and migration. To some extent, tetracycline inhibition of neutrophil functions is mimicked by the Ca2+ binding agents, EDTA and TMB-8. However, Ca2+ enrichment restored full function to EDTA- and TMB-8-treated cells but not to tetracycline-treated neutrophils. This suggests that Ca2+ binding plays a role but is not the critical effect leading to tetracycline suppression of neutrophil functions. It has been suggested that tetracyclines can suppress leukocyte-associated tissue damage. Host tissues are protected from neutrophil-mediated damage by two mechanisms: 1. Neutrophil granule-associated enzymes are secreted in an inactive state; and, 2. tissues are protected from these enzymes by a potent inhibitor shield. Neutrophils can bypass these protective elements by activating enzymes and by destroying the shield through the synthesis of oxygen radicals. Therefore, tetracyclines may suppress neutrophil-mediated tissue damage by inhibiting their migration and degranulation and, potentially more importantly, by suppressing synthesis of oxygen radicals.(ABSTRACT TRUNCATED AT 250 WORDS)

Low-dose doxycycline therapy: effect on gingival and crevicular fluid collagenase activity in humans

Tetracyclines are now recognized to have non-antimicrobial properties with therapeutic potential--for example, these agents can inhibit pathologic collagenolysis by blocking mammalian collagenases and other matrix-degrading metalloproteinases. In the current study, adult human subjects with moderate chronic periodontitis were administered specially formulated capsules of doxycycline, containing lower-than-usual amounts of this semi-synthetic tetracycline, on a daily basis for 2 weeks prior to a full-thickness flap procedure; control subjects were administered placebo capsules. The gingiva excised during this surgical procedure were extracted, the extracts partially purified and analyzed for collagenase activity using [3H-methyl] collagen as substrate and the techniques of SDS-PAGE/fluorography or liquid scintillation spectrometry. In the absence of any drug pre-treatment, or after a 2-wk regimen of placebo capsules, the gingival extracts exhibited pathologically-excessive mammalian collagenase activity. The 2-wk regimen of low-dose doxycycline capsules reduced this activity by approximately 60-80% (p less than 0.05 and less than 0.01, respectively); in vitro exposure of the gingival extract to doxycycline also inhibited its collagenase activity. Collagenase activity in the crevicular fluid of periodontal pockets of an additional group of subjects was also significantly reduced, as was the severity of inflammation at the same gingival sites. The results suggest that a regimen of low-dose doxycycline capsules may provide a safe (other studies indicate that this regimen may not induce tetracycline resistance in the subgingival plaque) and effective adjunct to instrumentation therapy in the management of pathologic collagenolysis in the periodontal patient. However, further studies are necessary to confirm this hypothesis.

Reviewing nonsurgical periodontal therapy

Selection of the appropriate case and clinical competency in treatment modalities results in success in nonsurgical periodontal therapy. The patient with early periodontitis with significant local factors in the form of professionally accessible plaque and calculus is the most receptive to nonsurgical periodontal treatment. The clinician must make decisions centering around the important question, "Can the patient, or moreover, can the therapist delivering the debridement, gain access to the microbial subgingival plaque on a frequent basis below the host defense threshold of the respective patient?" If the answer is "yes," nonsurgical periodontal therapy will be rewarding. If the answer is "no," other modalities such as periodontal surgery must be instituted.

Effect of minocycline on subgingival plaque bacteria

The effects of minocycline on subgingival plaque samples from patients with chronic periodontitis were investigated in vitro. Minocycline concentrations as low as 1.0 microgram/ml inhibited 95.7% of the cultivable bacteria in the samples but 256 micrograms/ml was necessary to inhibit all of the cultivable bacteria in the samples. Although up to 99.9% of bacteria in the plaque samples were killed by a 6 h exposure to 8.0 micrograms/ml of minocycline, large numbers of viable bacteria remained. These results imply that adequate reductions in the numbers of viable subgingival plaque bacteria are unlikely to occur after exposure to minocycline at concentrations attainable in gingival crevicular fluid after systemic administration.

Tetracycline administration normalizes the structure and acid phosphatase activity of osteoclasts in streptozotocin-induced diabetic rats

Diabetes induces osteopenia, which is characterized by a deficiency of osteoid and decreased activity of osteoblasts. We recently found that tetracyclines prevent the loss of osteoid and bone matrix and the degeneration of osteoblasts in diabetic rats by a mechanism independent of their antimicrobial efficacy. However, bone remodeling requires the activity of osteoclasts as well as osteoblasts. To determine the in vivo effects of tetracycline on osteoclasts in long bones, either a tetracycline (minocycline, TC) or its chemically modified non-antibiotic analogue (CMT), 4-de-dimethylaminotetracycline, was administrated daily to streptozotocin-induced diabetic rats by oral intubation. After 21 days, the rats were perfusion-fixed with a mixture of formaldehyde and glutaraldehyde, and the humeri were dissected and processed for ultracytochemical demonstration of acid trimetaphosphatase (ACPase) activity. In untreated non-diabetic (control) rats, the osteoclasts at the zone of provisional ossification exhibited abundant mitochondria and cisterns of rough endoplasmic reticulum (RER) throughout the cytoplasm, prominent stacks of Golgi membranes, and lysosomes in the perinuclear cytoplasm, and numerous various pale vacuoles in the cytoplasmic area adjacent to well-developed ruffled border. Intense ACPase activity was observed in the Golgi saccules, lysosomes, pale vacuoles, and the extracellular canals of ruffled border. The reaction products were also noted along the resorbing bone surfaces associated with the osteoclast ruffled border. The osteoclasts in the untreated diabetic rats showed a cytoplasmic organization similar to that of the non-diabetic control rats, but showed little or no ruffled border which was replaced by a broad clear zone in some of these cells. However, most of the osteoclasts on bone matrix in the diabetics were devoid of both a ruffled border and a clear zone. ACPase activity was detected in the osteoclast cytoplasm of diabetic rat, as in the controls, but to a much lesser extent along the broad clear zone facing the resorbing bone surfaces. The osteoclasts in TC-treated diabetic rats possessed both a clear zone and a small ruffled border. However, in some cases, they lacked both structures reminiscent of the untreated diabetic cells. The osteoclasts of CMT-treated diabetic rats exhibited structural and enzymatic features essentially identical to those of the non-diabetic control rats. These results suggest that the diabetes-induced osteopenia results, at least in part, from degeneration of osteoclasts (as well as atrophic osteoblasts) and that tetracyclines may be effective in preventing these abnormalities by a mechanism not dependent on the drugs' antimicrobial properties.

Minocycline-treatment of diabetic rats normalizes skin collagen production and mass: possible causative mechanisms

Daily minocycline-treatment of streptozotocin-induced diabetic rats not only prevented a diabetes-caused atrophy of skin collagen mass (10-mos old rats), but also normalized skin collagen mass to match that of growing (ca. 1%/d) non-diabetic controls (4- and 5-mos old rats). The causative mechanism by which minocycline-treatment normalizes skin collagen mass must, in part, be related to a general anabolic effect on growth (body weight) because the effect on skin collagen mass correlates strongly to that on body weight. Consequently, a minocycline-stimulated increase of a systemic factor (such as insulin-like growth factor) is not unlikely. The anabolic effect of minocycline-treatment of diabetic rats is also expressed as a normalized cellular ribosome mass (an index of total protein synthetic capacity) and a normalized absolute rate of collagen production. (Calculation of an absolute rate was justified by an apparent maximum saturation of the prolyl-tRNA pool(s) of skin, maximum saturation obtained by the pool-flooding approach). The normalized skin ribosome amount does not, however, explain a selective effect of minocycline-treatment on collagen production as opposed to that for non-collagen protein, this selective effect measured as relative collagen production. To explain such selectivity, the inhibition of diabetes-induced excess skin collagenase activity seems unlikely. (This inference is based on results from a preliminary study indicating that recently [less than 2 h] synthesized collagen is not degraded by the excess collagenase in skin of diabetic rats). Thus, the principal collagen fraction acted on by pathologically excess collagenase might be collagen at a later stage (greater than 2 h after synthesis) in its life cycle. (Another possibility for the selective effect of minocycline on collagen production, as yet untested, is reduced intracellular procollagen degradation.) Overall, this is the first study aimed at discerning the mechanism(s) by which minocycline-treatment enhances the rate of collagen production in tissues of a diabetic rat. For future studies, the extent to which the positive effect on growth, ribosome mass, and rate of collagen production contributes to the change of collagen mass must, along with the known minocycline-inhibition of collagenase activity, be quantified. Such quantification is a prerequisite for evaluating the chemotherapeutic efficacy of minocycline-treatment on collagen-degradative diseases.

Effect of tetracycline and SnF2 on root resorption in replanted incisors in dogs

The present study was made to assess the effect of applying SnF2, tetracycline, or both, to root surfaces of extracted teeth prior to replantation. In five young adult beagles, a total of 18 mandibular incisors were extracted, bench dried for 45 min, and reimplanted in their respective sockets either after no further treatment or following treatment with 1% doxycycline HCl for 5 min, 1% SnF2 for 5 min, or 1% SnF2 followed by 1% doxycycline HCl. After 4 wk of healing, the relative frequency of root resorption (surface resorption, inflammatory resorption and replacement resorption) was approximately 27% of the root surface in bench-dried as well as in doxycycline-treated specimens. By contrast, SnF2-treated and SnF2 + doxycycline-treated teeth showed less than 1% resorption. In the latter two specimen groups an inflammatory reaction in the periodontal ligament without resorption occurred with a frequency of 38.3% and 11.1%, respectively. The results indicate that application of SnF2 to the root surface prior to replantation effectively reduces resorptive processes during the first postoperative weeks. By subsequently treating the root surface with tetracycline, the adverse effect of SnF2 on periodontal connective tissue repair may be reduced.

Bacteriostatic effect of tetracycline in a temporary cement

Temporary crowns with subgingival margins can result in gingival inflammation. This inflammation is the result of plaque accumulating at the restoration-tooth interface and a change in the nature of that plaque to one associated with periodontitis. It was postulated that tetracycline incorporated in a slightly soluble cement would be released in the sulcus and decrease the amount, and improve the quality, of the subgingival microflora. The unknown was whether tetracycline is inactivated by any of the components of the temporary cement Temp Bond. To determine this concern, disks of Temp Bond cement with and without varying concentrations of tetracycline were anaerobically incubated in cultures of Bacteroides gingivalis. Results showed that tetracycline incorporated in Temp Bond at 10% by weight is highly bacteriostatic while retaining typical working properties of the cement.

Periodontal treatment by local drug delivery using resorbable base material

The effects of local drug delivery to the subgingival plaque flora using resorbable base material were evaluated by the study of microbial composition in periodontal pockets and clinical manifestations of disease.

In vitro, the drug used in this study was released within 24 hr from the hydroxypropylcellulose (HPC) strips. In vivo release of the drug from strips was also measured in nine patients who had, contralaterally, deep pockets of more than 5 mm. A tetracycline (TC)-containing HPC strip was inserted in one pocket, and a blank strip without TC was inserted in the other pocket. The amount of TC in the gingival crevicular fluid (GCF) 24 hr after insertion of the strip was significantly higher than that of the control.

Ten subjects, who had at least three pockets greater than 4 mm in depth, were selected from 50 volunteers after an initial examination. HPC strips containing TC, chlorhexidine (CH), and control (base material) were inserted into each pocket three times a week. Clinical and microbiological changes ascertained by darkfield microscopy were monitored over three weeks. Reduction of both probing depth and bleeding-on-probing was observed only in the pockets in which TC was administered. Changes of microbial composition of subgingival plaque were, however, found in both TC- and CH-treated pockets. The percentages of spirochetes and motile rods were remarkably reduced in these pockets.

Detection of high-risk groups and individuals for periodontal diseases. Systemic predisposition and markers of general health

The evidence for systemic predisposition to periodontal diseases is reviewed in relation to cellular and humoral immunity, drug therapy, diet and nutrition and stress. It is concluded that, apart from defects of polymorphonuclear leukocytes (PMN) and Ehlers-Danlos Syndrome, little firm evidence exists for other diseases, though insulin-dependent diabetes and acquired immune deficiency syndrome (AIDS) may accelerate and/or potentiate the damage of existing disease. The precise rôle of drugs, diet and nutrition and stress remain to be elucidated, but recent advances in these areas offer the prospect of assessing risk using carefully controlled studies.

Inhibition of epiphyseal cartilage collagenase by tetracyclines in low phosphate rickets in rats

Drugs in the tetracycline family can inhibit mammalian tissue collagenase both in vitro and in vivo by a mechanism that is independent of antibiotic action. The epiphyseal cartilages of rachitic rats contain extremely high levels of collagenase (CGase), and we have used this model to study further the phenomenon of tetracycline inhibition of tissue CGase. Rickets was induced in rats by phosphate/vitamin D deficiency and parameters of gross bone morphology, bone chemistry, and serum chemistry were evaluated in both rachitic and nonrachitic animals with and without treatment with oral tetracyclines (TETs). Minocycline (or doxycycline) partially suppressed the appearance of many of the expected changes in the rachitic animals, including gross bone hardness, growth plate widening, long bone length, suppression of weight gain, and decreased bone ash content. The effects were dose dependent and were associated with marked suppression of the enhanced CGase activity. Examination of collagen breakdown products by SDS-PAGE documented that the rachitic enzyme behaved like other mammalian collagenases including in vitro inhibition with minocycline 10-20 micrograms/ml and with a nonantibiotic tetracycline. No evidence of TET osseous toxicity was noted, and, in fact, administration of TET to nonrachitic animals had a mildly favorable effect on growth and development. TET suppression of CGase can be demonstrated in a well defined model system and this form of pharmacologic enzyme inhibition can be a useful probe for delineating the role of the enzyme in connective tissue pathology.

A non-antibacterial chemically-modified tetracycline inhibits mammalian collagenase activity

Tetracyclines (including the semi-synthetic analogues, minocycline and doxycycline) are considered useful adjuncts in periodontal therapy because they suppress Gram-negative periodontopathogens. Recently, these antibiotics were found to inhibit mammalian collagenase activity, a property which may also be of therapeutic value. It has been suggested that the anti-collagenase properties of the tetracyclines are independent of their antibiotic efficacy. To advance this hypothesis further, we chemically converted tetracycline hydrochloride to its non-antimicrobial analogue, de-dimethylaminotetracycline. This chemically-modified tetracycline (CMT), although no longer an effective antibiotic, was found to inhibit the in vitro activity of collagenase from partially purified extracts of human rheumatoid synovial tissue and rachitic rat epiphysis. In a preliminary in vivo study, pathologically-excessive collagenase in skin and gingiva was induced by rendering adult male rats diabetic, and the oral administration of CMT to these rats significantly reduced the excessive collagenase activity in both tissues. Moreover, CMT administration did not affect the severe hyperglycemia in these rats but did prevent, at least in part, the diabetes-induced loss of body weight, skin weight, and skin collagen mass; these effects suggest a lack of toxicity in this animal model. A proposed clinical advantage of CMT over conventional tetracyclines, in the treatment of diseases characterized by excessive collagenolytic activity, is the lack of development of antibiotic-resistant micro-organisms during prolonged use. However, the consideration of clinical trials to support this hypothesis must await further laboratory and extensive toxicity tests.