Inhibition of recombinant human neutrophil collagenase by doxycycline is pH dependent

OBJECTIVE

To examine, as part of an evaluation of the role of matrix metalloproteinase (MMP) inhibition in the amelioration of cartilage damage by doxycycline, the effect of pH on the inhibition of activity and reduction in stability of recombinant human neutrophil collagenase (rhMMP-8) by doxycycline in vitro.

METHODS

After activation with trypsin, rhMMP-8 was assayed using a peptolide substrate and a colorimetric assay. The rate of hydrolysis in the presence and absence of 30 microM doxycycline was measured over a pH range of 6.5-7.9. The molecular weight changes that accompanied activation of the proenzyme by acetylphenylmercuric acetate (APMA) in the presence and absence of doxycycline at pH 6.9 and 7.5 were studied by Western blotting.

RESULTS

At pH values above 7.1, doxycycline inhibited the activity of the enzyme. At pH values below 7.1, no inhibition was observed. When doxycycline was present during activation with APMA at pH 7.5, significant amounts of small (< 30 kDa) fragments were generated. In contrast, when doxycycline was present during activation with APMA at pH 6.9, no small fragments were detected.

CONCLUSION

The ability of doxycycline to inhibit matrix rhMMP-8 activity or to promote its degradation is lost at pH values lower than 7. Although relatively high pH values may exist in adult articular in some pathological situations, at lower pH the effect of doxycycline on proenzyme levels in the extracellular matrix may be due to an effect on the regulation of synthesis of the proenzyme, rather than to direct inhibition of the active enzyme or reduction in the level of enzyme by proteolysis.

Effects of self-care education on the health status of inner-city patients with osteoarthritis of the knee

OBJECTIVE

To evaluate a concise program of self-care education delivered by an arthritis nurse specialist as an adjunct to primary care for inner-city patients with knee osteoarthritis (OA).

METHODS

An attention-controlled clinical trial; 211 inner-city patients with knee OA were assigned arbitrarily to education (E) or attention-control (AC) conditions. Group E received an individualized 30-60-minute educational intervention that emphasized nonpharmacologic management of joint pain, preservation of function by problem-solving, and practice of principles of joint protection. Brief telephone contacts 1 week and 4 weeks later monitored and reinforced new self-care activities. Group AC viewed a 20-minute standardized public education presentation on arthritis and received followup telephone calls (only to encourage continued participation in the study). Outcomes included the Health Assessment Questionnaire (HAQ) Disability and Discomfort Scales, 10-cm visual analog scales measuring knee pain at rest and while walking, and the Quality of Well-Being (QWB) scale. Assessments were made at baseline and at 4-month intervals for 1 year.

RESULTS

A total of 165 subjects (78%) completed all assessments. After control for baseline status, group E had significantly lower scores for disability and resting knee pain throughout the year of postintervention followup (P < 0.05 for both). Effects were somewhat discordant. By 12 months, functional benefits had begun to wane, while the effect on resting knee pain had grown. The overall effects of education on walking knee pain, overall joint pain (by HAQ), and general health status (by QWB) were not significant.

CONCLUSION

Self-care education for inner-city patients with knee OA, delivered as an adjunct to primary care, was found to result in notable preservation of function and control of resting knee pain. The magnitude of the observed effects compares well with those of more labor-intensive and time-consuming intervention models. However, more sustained preservation of function and consistent effects on pain may require prolonged, more proactive followup, either by the patient educator or by a trained clinical assistant dedicated to the task of supporting self-care by patients with knee OA.

Quadriceps weakness and osteoarthritis of the knee

BACKGROUND

The quadriceps weakness commonly associated with osteoarthritis of the knee is widely believed to result from disuse atrophy secondary to pain in the involved joint. However, quadriceps weakness may be an etiologic factor in the development of osteoarthritis.

OBJECTIVE

To explore the relation between lower-extremity weakness and osteoarthritis of the knee.

DESIGN

Cross-sectional prevalence study.

SETTING

Population-based, with recruitment by random-digit dialing.

PARTICIPANTS

462 volunteers 65 years of age or older.

MEASUREMENTS

Radiographs of the knee were graded for the presence of osteoarthritis. Knee pain and function were assessed with the Western Ontario and McMaster Universities Arthritis Index, the strength of leg flexors and extensors was assessed with isokinetic dynamometry, and lower-extremity lean tissue mass was assessed with dual-energy x-ray absorptiometry.

RESULTS

Among participants with osteoarthritis, quadriceps weakness, but not hamstring weakness, was common. The ratio of extensor strength to body weight was approximately 20% lower in those with than in those without radiographic osteoarthritis. Notably, among women with tibiofemoral osteoarthritis, extensor weakness was present in the absence of knee pain and was seen in participants with normal lower-extremity lean mass (extensor strength, 30.1 lb-ft for those with osteoarthritis and 34.8 lb-ft for those without osteoarthritis; P < 0.001). After adjustment for body weight, age, and sex, lesser quadriceps strength remained predictive of both radiographic and symptomatic osteoarthritis of the knee (odds ratio for prevalence of osteoarthritis per 10 lb-ft loss of strength, 0.8 [95% CI, 0.71 to 0.90] for radiographic osteoarthritis and 0.71 [CI, 0.51 to 0.87] for symptomatic osteoarthritis).

CONCLUSION

Quadriceps weakness may be present in patients who have osteoarthritis but do not have knee pain or muscle atrophy; this suggests that the weakness may be due to muscle dysfunction. The data are consistent with the possibility that quadriceps weakness is a primary risk factor for knee pain, disability, and progression of joint damage in persons with osteoarthritis of the knee.

Serial kinematic analysis of the canine hindlimb joints after deafferentation and anterior cruciate ligament transection

OBJECTIVE AND DESIGN

Transection of the anterior cruciate ligament 2 weeks after ipsilateral hindlimb deafferentation leads to osteoarthritis of the knee joint within 3 weeks. We analyzed the gait of six dogs that underwent this procedure in order to identify kinematic changes that could account for this rapid joint degeneration. All animals were video taped, 1, 3, 6, 9 and 13 weeks after surgery while they trotted on a treadmill.

RESULTS

In each dog, extension of the hip, knee and ankle joints of the unstable limb was increased, and the yield phase of the unstable knee was delayed or attenuated. When killed, five of six dogs showed a large full-thickness cartilage ulcer on the distal and/or anterior surface of the medial femoral condyle of the unstable knee; in the sixth dog, a smaller ulcer was observed. However, the severity of pathology in each individual was not obviously related to difference among the dogs in postoperative joint kinematics.

CONCLUSIONS

These data, and results of prior studies in humans and dogs, suggest that knee hyperextension resulting from limb deafferentation, and knee instability resulting from anterior cruciate ligament transection, operate in concert to create a mechanical environment (i.e., increased tibiofemoral separation and changes in the loading of articular surfaces) that results in rapid joint breakdown.

Design and conduct of clinical trials in osteoarthritis: preliminary recommendations from a task force of the Osteoarthritis Research Society

In 1994, a combined committee of the World Health Organization and the International League of Associations for Rheumatology published recommendations for clinical trials for 2 classes of agents for treatment of osteoarthritis (OA) that relieved symptoms but differed in their onset and duration of response, and a third class of agents that may alter the disease process. Recently, the European Group for the Respect of Ethics and Excellence in Science made recommendations for methods to be used in the registration of drugs for OA. Following the 2nd international meeting of the Osteoarthritis Research Society in December 1994, a task force was convened to develop recommendations for the design and conduct of clinical trials in patients with OA. The Task Force had several meetings over the past 16 months, resulting in the preliminary recommendations summarized here.

In vivo observations of hydraulic stiffening in the canine femoral head

The role that intertrabecular contents and their boundary conditions have on the dynamic mechanical response of canine femoral heads was investigated in vivo. Femoral heads from paired intact hind limbs of canine specimens were subjected to a sinusoidal strain excitation at physiologic frequencies, in the cranio-caudal direction. The fluid boundary conditions for the contralateral limbs were changed by predrilling through the lateral femoral cortex and into the femoral neck. The drilling procedure did not invade the head itself. This femoral head fluid boundary alteration reduced the stiffness by 19 percent for testing at 1 Hz. The results of this study demonstrate that fluid stiffening occurs in vivo as previously observed ex vivo.

Bone scintigraphy in the canine cruciate deficiency model of osteoarthritis. Comparison of the unstable and contralateral knee

OBJECTIVE

To examine the effects on 99mTc medronate (MDP) bone scintigraphy of unilateral anterior cruciate ligament (ACL) transection in the unstable and contralateral knee of dogs.

METHODS

Bone scintigraphy was performed in 5 dogs at baseline and 6 and 12 weeks after ligament transection, with images of both knees obtained 3-4 h after intravenous injection of the radionuclide. An image of the T4-T5 vertebral region was also acquired as an internal standard. In 3 additional dogs, scintigraphy was performed at baseline and 5 1/2 weeks after sham ACL transection.

RESULTS

A marked increase in uptake of 99mTc MDP was seen in the unstable knee. In contrast, in all but one case uptake in the contralateral knee did not increase significantly. Sham ligament transection had no effect on uptake of the radionuclide.

CONCLUSION

Changes occur in subchondral bone as well as in articular cartilage in the unstable knee in this model. The bony changes, which could be either primary or secondary to early changes in the biomechanical properties of the cartilage, may contribute to the pathogenesis of cartilage damage. No appreciable effects on bone turnover in the contralateral knee could be proved in this study.

Accelerated clearance of albumin from the osteoarthritic knee: implications for interpretation of concentrations of "cartilage markers" in synovial fluid

OBJECTIVE

The magnitude of articular cartilage destruction or repair in osteoarthritic (OA) joints has been deduced in some studies from the synovial fluid (SF) concentration of proteins derived from the extracellular matrix of the cartilage, without regard to the low grade synovitis that is often present in this disease. We examined the clearance kinetics of albumin, as a surrogate for cartilage derived proteins, from OA and control joints in an established canine model.

METHODS

Twelve weeks after the left anterior cruciate ligament of 6 normal dogs was transected, 131I albumin (RISA) was injected into the contralateral (control) knee. Surface radioactivity was monitored for 7 h, and SF was then aspirated to determine the SF RISA concentration and leukocyte count, and calculate the volume of distribution (VD) and clearance of RISA. One week later, RISA was injected into the cruciate deficient knee and these measurements were repeated, then the intensity of synovial inflammation and severity of cartilage changes of OA in both knees were assessed.

RESULTS

Synovitis and articular cartilage ulceration were seen only in the cruciate-deficient OA knee, in which the mean SF leukocyte count (1570/mm3), thickness of the synovial intima (mean = 30 microns), and severity of synovial mononuclear cell infiltration (mean = 13,500 cells/mm2) significantly exceeded those in the contralateral knee (850/mm3, 13 microns, 1400 cells/mm2; p < or = 0.01 in each case). In each dog, RISA VD in the OA knee was higher than in the contralateral knee (mean = 9.2 +/- 3.6 and 3.7 +/- 0.9 ml, respectively; p = 0.008) and RISA clearance rate in the OA knee exceeded that in the contralateral knee (3.8 +/- 1.5 and 1.4 +/- 0.3 microliters/min, respectively; p = 0.009).

CONCLUSION

Accelerated clearance of protein from the OA joint with low grade synovitis could significantly affect the SF concentration of cartilage derived proteins. Therefore, inferences about the effect of a therapeutic agent on cartilage metabolism based upon changes in the concentration of a protein in serial samples of OA SF may be misleading unless protein clearance kinetics have been determined.

Activation of recombinant human neutrophil procollagenase in the presence of doxycycline results in fragmentation of the enzyme and loss of enzyme activity

OBJECTIVE

To determine if reduction of collagenase activity in vitro by doxycycline (doxy) is related to activation of the proenzyme, and to determine how exogenous Ca++ and Zn++ affect the reduction.

METHODS

Recombinant human neutrophil procollagenase was activated with trypsin or APMA. Activity was assayed on a small peptolide substrate or on 14C-acetylated collagen fibers. The molecular weight of the proenzyme, active enzyme, and enzyme fragments was determined by Western blotting, using a polyclonal antiserum raised against the recombinant proenzyme. Similar experiments were performed in the presence of EDTA, EGTA, 1,10-phenanthroline, or doxy. The effects of exogenous Ca++ and Zn++ were also tested.

RESULTS

Doxy inhibited activity of the enzyme against both substrates. If the drug was present during activation, the yield of activity was lower than when it was added after activation of the proenzyme. Western blotting showed that activation in the presence of doxy resulted in the appearance of lower molecular weight fragments and accumulation of less active enzyme. APMA generated prominent 28- and 26-kd fragments while trypsin cleavage yield 40- and 30-kd fragments. Fragmentation of the enzyme also occurred in the presence of EDTA or EGTA, but not 1,10-phenanthroline. It was prevented by Ca++ concentrations greater than 50 mM, but was not altered by addition of Zn++ in concentrations as high as 500 microM. Inhibition of collagenase activity by doxy could be overcome by 100 mM Ca++, but addition of Zn++ had no effect.

CONCLUSION

These data suggest that doxy alters the conformation of procollagenase or collagenase by binding enzyme-associated Ca++, rendering the proteins more susceptible to proteolysis and resulting in irreversible loss of enzyme protein.

Effects of oral doxycycline administration on histomorphometry and dynamics of subchondral bone in a canine model of osteoarthritis

OBJECTIVE

To determine whether oral administration of doxycycline, in a dose that inhibits cartilage breakdown in a canine cruciate deficiency model of osteoarthritis (OA), affected formation or resorption of subchondral bone.

METHODS

Ten healthy adult mongrel dogs underwent transection of the left anterior cruciate ligament. Five were given doxycycline, 3.5 mg/kg/day, orally, from the day after surgery until they were sacrificed 6 weeks later; the other 5 dogs served as positive OA controls. Three weeks before sacrifice, each dog was given an intravenous injection of the fluorochrome label, calcein, on each of 2 consecutive days; 10 days later, the injection regimen was repeated. At sacrifice, samples of bone from the medial femoral condyle of both knees of each dog were obtained for staining with Villanueva tetrachrome to localize the fluorochrome label and McNeal's tetrachrome for measurement of osteoid and cell counts.

RESULTS

Cruciate deficiency resulted in a marked decrease in bone mass, with increased osteoclastic activity and increased bone formation. Doxycycline treatment did not significantly affect either bone formation or bone resorption.

CONCLUSION

Doxycycline protects against joint breakdown in this OA model via inhibition of matrix metalloproteinases in articular cartilage, rather than through an effect on subchondral bone.

Nonsurgical management of osteoarthritis, with an emphasis on nonpharmacologic measures

Osteoarthritis is treated primarily with nonsteroidal anti-inflammatory drugs. Concern is growing, however, among physicians and patients about the gastrointestinal side effects of these agents. Nonpharmacologic measures are underused in the treatment of osteoarthritis; isometric exercise and provision of social support may be as effective as nonsteroidal anti-inflammatory drugs in reducing pain and improving mobility in patients with knee osteoarthritis. Recent data argue persuasively for a change in our strategy for treatment of patients with osteoarthritis: the treatment program should emphasize nonpharmacologic measures, with drugs used in an adjunctive role. Only when this approach is not effective should nonsteroidal anti-inflammatory drugs be prescribed, and then, in the lowest dose needed for symptomatic relief.

Practical management of osteoarthritis. Integration of pharmacologic and nonpharmacologic measures

Pharmacotherapy should play an adjunctive role to nonpharmacologic measures in the overall management of patients with symptoms due to osteoarthritis. Patients should be instructed in how to rest or unload involved joints; protect them through appropriate manipulation of their environment and appropriate methods of lifting and bending; and maintain and improve muscle strength and flexibility to ensure joint stability and prevent contractures. In most patients, acetaminophen in doses of up to 4 g/d is preferable to nonsteroidal anti-inflammatory drugs (NSAIDs) as a first-choice agent because of its lower toxicity. If NSAIDs are used, they should be prescribed initially in lower (analgesic) doses. Ibuprofen may be the preferred initial NSAID because it can be given in low doses for short durations, has been associated with lower rates of gastrointestinal tract side effects, and is inexpensive.

Guidelines for the medical management of osteoarthritis. Part II. Osteoarthritis of the knee. American College of Rheumatology

Treatment of patients with OA of the knee should be individualized and tailored to the severity of the symptoms. In individuals with mild symptomatic OA, treatment may be limited to patient education, physical and occupational therapy and other nonpharmacologic modalities, and pharmacologic therapy including non-opioid oral and topical analgesics. In patients who are unresponsive to this treatment regimen, the use of NSAIDs in addition to nonpharmacologic therapy is appropriate unless medically contraindicated. Judicious use of intraarticular steroid injections has a role either as monotherapy or an adjunct to systemic therapy in patients with knee OA who have symptomatic effusions. The role of joint lavage and arthroscopic debridement in patients with OA of the knee who are unresponsive to conservative medical therapy needs further study, and these procedures cannot be routinely recommended for all patients at this time. Patients with severe symptomatic OA of the knee require an aggressive approach to decreasing pain, increasing mobility, and decreasing functional impairment; such patients may benefit from orthopedic consultation and evaluation for osteotomy or total joint arthroplasty.

Guidelines for the medical management of osteoarthritis. Part I. Osteoarthritis of the hip. American College of Rheumatology

Treatment of patients with OA of the hip should be individualized and tailored to the severity of the disease. In individuals with mildly symptomatic disease, treatment may be limited to patient education, physical and occupational therapy, other nonpharmacologic modalities, and drug therapy with a non-opioid oral analgesic. In patients who are unresponsive to this treatment regimen, the use of an NSAID in addition to nonpharmacologic therapy is appropriate unless it is medically contraindicated. Patients with severe symptomatic OA of the hip require an aggressive approach to decreasing pain, increasing mobility, and improving function; such patients may benefit from orthopedic consultation and evaluation for osteotomy or total joint arthroplasty.

Effects of synovial fluid hyaluronan concentration and molecular size on clearance of protein from the canine knee

OBJECTIVE

The synovial fluid (SF) concentration of proteins (or fragments thereof) derived from the articular cartilage may reflect the processes of cartilage breakdown or repair within an arthritic joint and, hence, serve as a marker of these processes. Because changes in the clearance kinetics of marker molecules in SF would invalidate the assumption that their concentration in SF is directly proportional to turnover of the cartilage matrix, we investigated whether reduction in the concentration and/or molecular size of hyaluronan (HA) in joint effusions affects clearance of albumin from the canine knee.

METHODS

The volume of distribution and clearance kinetics of radioiodinated serum albumin (RISA) were determined in normal dogs after injection of the knee with HA preparations whose concentration (3.0-0.03 mg/ml) and average molecular weight (0.2-6.1 x 10(6) Da) resembled those seen in synovial effusions, and which increased by roughly 270% the volume of fluid in the joint space.

RESULTS

In knees injected with a physiologic concentration (3.0 mg/ml) of high molecular weight HA, the RISA distribution volume (2.8 ml) and clearance rate (1.7 microliters/min) slightly exceeded those in knees in which the SF HA concentration was reduced 55-62% by injection of 0.3-0.03 mg/ml HA, but not those in knees in which the average molecular weight of the SF HA was reduced 84% by injection of exogenous HA with a molecular weight of 2.4 x 10(5) Da.

CONCLUSION

Our data suggest that SF HA is a relatively minor determinant of the kinetics of RISA clearance from the joint, and the changes in HA content seen in joint effusions are unlikely to confound interpretation of the concentration of marker molecules in SF.

Cartilage metabolism--a response

Images

Even low-grade synovitis significantly accelerates the clearance of protein from the canine knee. Implications for measurement of synovial fluid "markers" of osteoarthritis

OBJECTIVE

In recent studies, the synovial fluid concentration of molecules derived from the extracellular matrix of articular cartilage has been used to deduce the magnitude of cartilage destruction or repair in osteoarthritic (OA) joints. Because low-grade synovitis is often present in such joints, we assessed the effect of synovial inflammation on the clearance of a prototypical protein, albumin, from synovial fluid.

METHODS

131I-labeled albumin (RISA) was injected into 1 (control) knee of each of 14 dogs. The concentration of RISA in synovial fluid aspirated 7 hours after the injection and serial measurements of surface radioactivity were used to calculate the volume of distribution (Vd) and clearance of RISA. One week later, synovitis was induced in the contralateral knee by intraarticular injection of various quantities of calcium pyrophosphate dihydrate (CPPD) crystals, after which RISA was injected into that joint and these measurements were repeated.

RESULTS

Intraarticular injection of 500 micrograms of CPPD crystals produced intense synovitis, with a mean synovial fluid white blood cell (WBC) count of 43,200 cells/mm3, and values for RISA Vd and RISA clearance (36.5 ml and 33.7 microliters/minute) were much higher than those for saline-injected control knees (2.7 ml and 1.5 microliters/minute, respectively). Injection of 0.5 microgram of CPPD also produced marked synovitis and values for Vd and RISA clearance that were 2-3-fold greater than those in the contralateral knee. The low-grade synovitis produced by only 0.05 microgram of CPPD, which resulted in synovial fluid WBC counts as low as 1,000-2,000 cells/mm3, was accompanied by increases in the clearance and Vd of RISA to levels approximately 40% and approximately 80% higher, respectively, than those for the contralateral knee.

CONCLUSION

Even mild synovitis, as seen in OA, may significantly increase the clearance of a protein from the joint. Synovitis is a significant variable which must be considered in studies of putative chondroprotective drugs if conclusions about the effects of drugs on cartilage metabolism are to be drawn from changes in the synovial fluid concentration of a "marker" protein.

A whole-cell Candida albicans assay for the detection of inhibitors towards fungal cell wall synthesis and assembly

A whole-cell C. albicans screen was designed to identify novel inhibitors interacting with the synthesis, assembly and regulation of the fungal cell wall. C. albicans was grown in a paired broth assay in 96-well plates with natural product extracts or pure chemical compounds in the presence and absence of the osmotic stabilizer, sorbitol. Growth was visually examined over a 7-day period and scored into different growth categories. Positives from the sorbitol rescue were then examined under the microscope for morphological alterations and grouped into several morphological classes. Sorbitol protection and cell morphology were indicators of novel antifungal agents from natural product extracts and pure compounds.