Protective effects of a cathepsin K inhibitor, SB-553484, in the canine partial medial meniscectomy model of osteoarthritis

OBJECTIVE

Cathepsin K (cat K), a cysteine protease expressed in osteoclasts, chondrocytes and synovial fibroblasts, degrades several bone and cartilage matrix components suggesting its potential role in osteoarthritis (OA). We investigated the effects of SB-553484, an inhibitor of cat K, on lesion severity and biomarkers of collagen degradation in the canine partial medial meniscectomy model.

METHODS

A partial medial meniscectomy was performed in mature female beagle dogs. Animals were dosed orally with vehicle or SB-553484 at 50mg/kg BID for 28 days. The femorotibial joints were evaluated for gross and microscopic histological changes. Biomarkers of collagen degradation were also analyzed.

RESULTS

In dogs treated with SB-553484, subjective gross and calculated degeneration scores decreased significantly by 29% and 46%, respectively. Histopathologic evaluation demonstrated that the summed tibial degeneration score decreased significantly by 21%. Inhibition of tibial cartilage degeneration was significant in zone 1 (32%) and the depth ratio of any tibial matrix change was decreased significantly by 28%. Urinary biomarkers of bone and cartilage degradation were also significantly reduced.

CONCLUSION

Treatment with SB-553484 resulted in mild to moderate beneficial effects on gross and histopathological parameters. Reduction of biomarkers of collagen type I and II degradation indicated a direct effect of the compound on bone and cartilage. These data suggest that the prevention of cartilage degradation by cat K inhibition may represent a valid strategy for pharmacological intervention in OA and that monitoring collagen degradation biomarkers may provide an indication of the protective effects of inhibition of bone and cartilage degradation.

Disease-modifying activity of SB 273005, an orally active, nonpeptide alphavbeta3 (vitronectin receptor) antagonist, in rat adjuvant-induced arthritis

OBJECTIVE

To evaluate the effects of SB 273005, a potent, orally active nonpeptide antagonist of the integrin avbeta3 vitronectin receptor, on joint integrity in rats with adjuvant-induced arthritis (AIA).

METHODS

Male Lewis rats with AIA were orally dosed either prophylactically (days 0-20) or therapeutically (days 10-20) with SB 273005. Efficacy was determined by measurement of paw inflammation, assessment of bone mineral density using dual-energy x-ray absorptiometry (DEXA), magnetic resonance imaging (MRI), and histologic evaluation.

RESULTS

SB 273005 is a potent antagonist of the closely related integrins, avbeta3 (Ki = 1.2 nM) and alphavbeta5 (Ki = 0.3 nM). When SB 273005 was administered prophylactically to AIA rats twice per day, it inhibited paw edema at doses of 10, 30, and 60 mg/kg, by 40%, 50%, and 52%, respectively. Therapeutic administration twice daily was also effective, and a reduction in paw edema was observed at 30 mg/kg and 60 mg/kg of the antagonist (by 36% and 48%, respectively). SB 273005 was also effective when administered once per day, both prophylactically and therapeutically. Significant improvement in joint integrity in treated rats was shown using DEXA and MRI analyses. These findings were confirmed histologically, and significant protection of bone, cartilage, and soft tissue was observed within the joint.

CONCLUSION

Symptoms of AIA in rats were significantly reduced by either prophylactic or therapeutic treatment with the alphavbeta3 antagonist, SB 273005. Measurements of paw inflammation and of bone, cartilage, and soft tissue structure indicated that this compound exerts a protective effect on joint integrity and thus appears to have disease-modifying properties.

Differential effects of SB 242235, a selective p38 mitogen-activated protein kinase inhibitor, on IL-1 treated bovine and human cartilage/chondrocyte cultures

The p38 MAP kinase inhibitor, SB 242235, was evaluated for its effects on the metabolism of bovine and human cartilage and primary chondrocyte cultures. SB 242235 had no effect on proteoglycan synthesis (PG) in bovine articular cartilage explants (BAC), as measured by [(35)S]-sulfate incorporation into glycosaminoglycans (GAGs). In addition, the compound had no effect on IL-1 alpha-induced GAG release from these cultures. However, there was a potent, dose-dependent inhibition of nitric oxide (NO) release from IL-1 alpha-stimulated BAC with an IC(50)of approximately 0.6 microM, with similar effects observed in primary chondrocytes. The effect on BAC was time dependent, and mechanistically did not appear to be the result of inhibition of protein kinase C (PKC), protein kinase A (PKA) or MEK-1. The effect on NO release in bovine chondrocytes was at the level of inducible nitric oxide synthase (iNOS) gene expression, which was inhibited at similar concentrations as nitrite production. In primary human chondrocytes, IL-1 beta induction of p38 MAP kinase was inhibited by SB 242235 with an IC(50)of approximately 1 microM. Surprisingly, however, treatment of IL-beta-stimulated human cartilage or chondrocytes with SB 242235 did not inhibit either NO production or the induction of iNOS. On the other hand, the natural product hymenialdisine (HYM), a protein tyrosine kinase (PTK) inhibitor, inhibited NO production and iNOS in both species. In contrast to the differential control of iNOS, PGE(2)was inhibited by SB 242235 in both IL-1-stimulated bovine and human chondrocyte cultures. These studies indicate that there are species differences in the control of iNOS by p38 inhibitors and also that different pathways may control IL-1-induced proteoglycan breakdown and NO production.

Disease-modifying activity of SB 242235, a selective inhibitor of p38 mitogen-activated protein kinase, in rat adjuvant-induced arthritis

OBJECTIVE

To evaluate the effects of SB 242235, a potent and selective inhibitor of p38 mitogen-activated protein (MAP) kinase, on joint integrity in rats with adjuvant-induced arthritis (AIA).

METHODS

Male Lewis rats with AIA were orally treated either prophylactically (days 0-20) or therapeutically (days 10-20) with SB 242235. Efficacy was determined by measurements of paw inflammation, dual-energy x-ray absorptiometry for bone-mineral density (BMD), magnetic resonance imaging (MRI), microcomputed tomography (CT), and histologic evaluation. Serum tumor necrosis factor alpha (TNFalpha) in normal (non-AIA) rats and serum interleukin-6 (IL-6) levels in rats with AIA were measured as markers of the antiinflammatory effects of the compound.

RESULTS

SB 242235 inhibited lipopolysaccharide-stimulated serum levels of TNFalpha in normal rats, with a median effective dose of 3.99 mg/kg. When SB 242235 was administered to AIA rats prophylactically on days 0-20, it inhibited paw edema at 30 mg/kg and 10 mg/kg per day by 56% and 33%, respectively. Therapeutic administration on days 10-20 was also effective, and inhibition of paw edema was observed at 60, 30, and 10 mg/kg (73%, 51%, and 19%, respectively). Significant improvement in joint integrity was demonstrated by showing normalization of BMD and also by MRI and micro-CT analysis. Protection of bone, cartilage, and soft tissues was also shown histologically. Serum IL-6 levels were decreased in AIA rats treated with the 60 mg/kg dose of compound.

CONCLUSION

Symptoms of AIA in rats were significantly reduced by both prophylactic and therapeutic treatment with the p38 MAP kinase inhibitor, SB 242235. Results from measurements of paw inflammation, assessment of BMD, MRI, and micro-CT indicate that this compound exerts a protective effect on joint integrity, and thus appears to have disease-modifying properties.

Idoxifene, a novel selective estrogen receptor modulator, is effective in a rat model of adjuvant-induced arthritis

Idoxifene, a selective estrogen receptor modulator, was evaluated in male and female rats with adjuvant-induced arthritis (AA). AA was induced in Lewis rats with Mycobacterium butyricum in paraffin oil injected into the base of the tail, and the animals were treated with idoxifene prophylactically (days 0-21) or therapeutically (days 10-21). Efficacy was determined by measurements of paw inflammation, bone mineral content, and bone mineral density (BMD) with dual X-ray absorptiometry and by histological evaluation. Serum interleukin-6 levels were measured as a marker of the anti-inflammatory effects of the compound. Estrogen was included for comparison and was administered at 5 mg/kg, three times a week s.c. Prophylactic treatment of male AA rats with idoxifene at 10, 3, and 1 mg/kg and estrogen at 5 mg/kg significantly inhibited paw inflammation. There was improved joint integrity measured by BMD and reduced serum interleukin-6 levels in animals treated with 10 mg/kg/day idoxifene. Idoxifene and estrogen were as effective for AA in female Lewis rats as in male rats, significantly inhibiting paw inflammation and improving BMD. Histological evaluation of the tibiotarsal joints of female rats treated with 10 mg/kg showed protection of bone, cartilage, and soft tissue. Therapeutic treatment with either idoxifene or estrogen (starting on day 10 of disease) of male and female Lewis rats also was effective in reducing paw inflammation in these animals, although the effect was much less than that observed with the prophylactic dosing protocol.

Inhibition of interleukin-1-induced proteoglycan degradation and nitric oxide production in bovine articular cartilage/chondrocyte cultures by the natural product, hymenialdisine

The effects of hymenialdisine (SK&F 108752) were evaluated on interleukin-1 (IL-1)-induced proteoglycan (PG) degradation, PG synthesis, nitric oxide (NO) production, and inducible nitric oxide synthase (iNOS) gene expression in bovine articular cartilage (BAC) and/or cartilage-derived chondrocytes. Cartilage disks from 0- to 3-month-old calves were treated with IL-1alpha or retinoic acid. PG release was determined by measuring glycosaminoglycan release, and nitrite production was measured as a readout for NO. Inhibition of iNOS gene expression was measured by Northern blot analysis in IL-1alpha-stimulated, cartilage-derived chondrocytes. To measure PG synthesis, chondrocytes were established in alginate beads and treated with hymenialdisine, and then [(35)S]sulfate incorporation into PGs was determined. Hymenialdisine inhibited IL-1alpha-stimulated PG breakdown in BAC in a dose-related manner with an IC(50) of approximately 0.6 microM. Herbimycin, a protein tyrosine kinase inhibitor, also inhibited PG breakdown, whereas RO 32-0432, a protein kinase C inhibitor, had no effect. Both hymenialdisine and herbimycin also were able to inhibit retinoic acid-stimulated PG release. IL-1alpha-stimulated NO production in BAC was inhibited by hymenialdisine and herbimycin at similar concentrations. The effect on iNOS gene expression was determined by Northern blot analysis in chondrocytes grown in monolayer, and inhibition by hymenialdisine was observed with an IC(50) of approximately 0.8 microM. In chondrocytes cultured in alginate beads, IL-1alpha inhibited PG synthesis, whereas hymenialdisine stimulated synthesis at low concentrations (0.6 and 1.25 microM), and higher doses (2.5 microM) were not stimulatory. Compounds with this profile may have utility in the treatment of osteoarthritis.

SB 203580 inhibits p38 mitogen-activated protein kinase, nitric oxide production, and inducible nitric oxide synthase in bovine cartilage-derived chondrocytes

Nitric oxide (NO) is implicated in a number of inflammatory processes and is an important mediator in animal models of rheumatoid arthritis and in in vitro models of cartilage degradation. The pyridinyl imidazole SB 203580 inhibits p38 mitogen-activated protein (MAP) kinase in vitro, blocks proinflammatory cytokine production in vitro and in vivo, and is effective in animal models of arthritis. The purpose of this study was to determine whether SB 203580 could inhibit p38 MAP kinase activity, NO production, and inducible NO synthase (iNOS) in IL-1 stimulated bovine articular cartilage/chondrocyte cultures. The results indicated that SB 203580 inhibited both IL-1 stimulated p38 MAP kinase activity in isolated chondrocytes and NO production in bovine chondrocytes and cartilage explants with an IC50 value of approximately 1 microM. To inhibit NO production, SB 203580 had to be present in cartilage explant cultures during the first 8 h of IL-1 stimulation, and activity was lost when it was added 24 h following IL-1. SB 203580 did not inhibit iNOS activity, as measured by the conversion of arginine to citrulline, when added directly to cultures where the enzyme had already been induced, but had to be present during the induction period. Using a 372-bp probe for bovine iNOS we demonstrated inhibition of IL-1-induced mRNA by SB 203580 at both 4 and 24 h following IL-1 treatment. The iNOS mRNA levels were consistent with NO levels in 24-h cell culture supernatants of the IL-1-stimulated bovine chondrocytes used to obtain the RNA.

Disease-modifying activity of SK&F 106615 in rat adjuvant-induced arthritis. Multiparameter analysis of disease magnetic resonance imaging and bone mineral density measurements

OBJECTIVE

To evaluate the effect of SK&F 106615 on joint integrity in rats with adjuvant-induced arthritis (AIA).

METHODS

AIA was induced in Lewis rats on day 0, and the animals were treated either prophylactically (days 0-16 or days 0-23) or therapeutically (days 10-23) with SK&F 106615. Efficacy was determined by measurements of paw inflammation, bone mineral density (BMD) using dual x-ray absorptiometry, and magnetic resonance imaging (MRI). Joint integrity was also determined histologically, and serum interleukin-6 (IL-6) levels were measured as a marker of the antiinflammatory effects of the compound.

RESULTS

Prophylactic treatment (days 0-16) of AIA rats with SK&F 106615 significantly inhibited paw volume at doses of 545 mg/kg/day given orally on 5 days each week. Extensive evaluation of joint integrity in rats treated with SK&F 106615 20 mg/kg/day orally for 23 days showed inhibition of paw volume, normalization of BMD, and significant improvement in disease by MRI and histologic assessment compared with the AIA controls. Elevated levels of serum IL-6 in AIA rats were reduced dramatically by SK&F 106615. Therapeutic treatment (days 10-23) resulted in similar protective effects measured by paw inflammation, BMD, and MRI. In the therapeutic protocol, serum IL-6 appeared to be a more sensitive marker of antiinflammatory activity than paw edema.

CONCLUSION

Symptoms of AIA in rats are significantly reduced by prophylactic and therapeutic treatment with SK&F 106615. Of particular note, this compound appears to exert a protective effect on joint integrity and to have disease-modifying properties.

Effects of a novel azaspirane (SK&F 105685) on arthritic lesions in the adjuvant Lewis rat: attenuation of the inflammatory process and preservation of skeletal integrity

OBJECTIVE

To determine the effects of SK&F 105685 (N,N-dimethyl-8,8-dipropyl-2-azaspiro[4.5] decane-2-propanamine dihydrochloride) on the arthritic lesions in the tibiotarsal joint of adjuvant arthritic (AA) rats.

METHODS

Inhibition of hindpaw inflammation was measured by water displacement. The protective effects on joint integrity were determined by measuring radiographic and histological changes and by scanning electron microscopy.

RESULTS

Compared to AA control rats, SK&F 105685 suppressed hindpaw edema 64% or 41-54% in AA rats receiving 30 or 20 mg/kg/day, respectively. Radiographic evaluation showed marked decreases in soft tissue swelling and in the severity of skeletal tissue loss at the tibiotarsal joint in both dose groups. Histologically SK&F 105685 markedly attenuated the extent and severity of the inflammatory lesion and preserved the basic integrity of bone and cartilaginous tissues, including the content and distribution of proteoglycans of the articular cartilages. Cellular changes included decreases in the inflammatory infiltrate and in the number of osteoclasts and chondroclasts. Whereas AA control rats exhibited marked to severe loss (41-70%) of skeletal tissue mass, the loss in rats given 30 mg/kg SK&F 105685 was mild (< 20%). Scanning electron microscopy of the talus revealed only slight erosion of the articular cartilage and general preservation of the underlying bone. In contrast, in AA controls, there was marked erosion of the talar articular cartilage and severe loss of subchondral bone. Spleen cells from SK&F 105685 treated rats had a reduced capacity to respond to concanavalin A and contained suppressor cell activity as measured in a coculture assay.

CONCLUSION

Our studies show that SK&F 105685 has remarkable protective effects on the joints of AA rats and suggests that it may attenuate the overall inflammatory process and retard the degenerative loss of skeletal tissue in rheumatoid arthritis in humans.

Beneficial effects of SK&F 105685 in rat adjuvant arthritis: prophylactic and therapeutic effects on disease parameter progression

Prophylactic administration of SK&F 105685 (N, N-dimethyl-8,8,-dipropyl-2-azaspiro[4.5]decane-2-propanamine dihydrochloride) at 30 mg/kg/day inhibited hindpaw lesions in adjuvant arthritic (AA) rats following 16 (84% inhibition) and 24 (70% inhibition) days of treatment. In a therapeutic protocol, where dosing was initiated on day 10 after disease induction, SK&F 105685 (20 mg/kg/day) effectively halted disease progression, and the inflammatory lesion was suppressed by 70% following treatment for 20 days. Histological evaluation of the joint periarticular soft tissue, bone and articulation (joint space and joint surface) from therapeutically treated rats showed a clear beneficial effect. Most rats presented moderate lesions rather than the severe lesions seen in the AA animals. AA control rats and AA rats treated prophylactically or therapeutically with SK&F 105685 had significant and similar increases in their total white blood cell (WBC), neutrophil, monocyte and platelet counts. Although increases were seen in the absolute number of neutrophils and platelets, there were no differences in the levels of leukotriene B4 (LTB4) and hydroxyheptadecatrienoic acid (HHT), per cell when these cells were stimulated with the calcium ionophore A23187. These results, describing the beneficial effects of SK&F 105685 administered therapeutically to the AA rat, indicate that this compound possesses properties desirable of an anti-arthritic agent and may potentially modify the disease outcome.

Therapeutic activity of SK&F 105685, a novel azaspirane with suppressor-cell inducing activity

SK&F 105685, methotrexate (MTX) and chloroquine (CHL) were examined for their ability to inhibit paw inflammation in the adjuvant arthritic rat (AA) and for their ability to induce non-specific suppressor cells (SC) in the spleens of these animals. Compared to SK&F 105685 (84-90%) inhibition and MTX (91% inhibition) CHL, at the maximally tolerated dose, only inhibited paw lesions by 29%. MTX did not induce splenic SC activity and, despite the structural similarities between CHL and SK&F 105685, only the latter induced suppressor cells.

Effects of SK&F 105685, a novel anti-arthritic agent, on immune function in the dog

SK&F 105685 (N,N-dimethyl-8,8-dipropyl-2-azaspiro[4,5]decane-2-propanamine+ ++ dihydrochloride) is a novel azaspirane with beneficial activity in animal models of autoimmune disease such as adjuvant-induced arthritis and experimental encephalomyelitis in the Lewis rat and lupus-like disease in the MRL mouse. The activity of SK&F 105685 in these models is associated with the induction of non-specific suppressor cell (SC) activity as defined by the ability of cells from drug-treated animals to inhibit the proliferative response of lymphocytes from control animals to concanavalin A. To evaluate the immunotoxicologic potential of SK&F 105685, the effect on immune function of one month of dosing with 1 mg/kg/day of SK&F 105685 was examined in the dog. Differential blood cell counts and ex vivo immune function assays were performed using blood collected before dosing on days 1 (baseline), 15 and 29, of the study. Immune function assays were performed on spleen cells on day 30. Under the conditions of the study, SK&F 105685 displayed pharmacological activity as demonstrated by the induction of splenic SC activity. The drug did not affect the total number or relative percentages of the various white blood cell types present in peripheral blood and did not cause generalized immunosuppression. The ability of peripheral blood lymphocytes or spleen cells to produce IL-2 or proliferate in response to mitogenic stimulation was not affected by drug treatment. SK&F 105685 also failed to affect the candidacidal activity of polymorphonuclear leucocytes and spleen cells indicating that it is unlikely to compromise nonspecific resistance to infection. SK&F 105685 however, was able to inhibit the generation of a specific in vitro antibody response to sheep red blood cells (SRBC) by splenocytes from treated animals. Inhibition of the anti-SRBC antibody response was also observed upon addition of the drug to normal spleen cells. Addition of the drug at different time points during the culture period indicated that SK&F 105685 was interfering with an event(s) occurring during the first 72 h of culture. Taken together, these results suggest that, in a therapeutic setting, SK&F 105685 is unlikely to compromise the immune status of the host as it can down-regulate a specific immune response without causing generalized immunosuppression.

Inhibition of autoimmune disease and the generation of suppressor cells by spirogermanium: a biological profile similar to total lymphoid irradiation

Oral administration of spirogermanium (Sg), inhibits the development of immune-mediated hindpaw inflammation in the rat model of adjuvant arthritis (AA) and DTH responses to PPD (30 mg/kg/day). A similar dosing protocol inhibits hindleg paralysis in experimental autoimmune encephalomyelitis (EAE). The spleens of these animals and those of normal rats contain radiation resistant (2000 R) non-specific suppressor cells (SC) which bear some similarity to those generated following total lymphoid irradiation (TLI). These cells do not appear to be mature T cells, they are partially adherent to plastic, sephadex G10 and nylon wool, insensitive to indomethacin and are enriched in a 1.07 g/ml fraction of a Percoll density gradient.

Immunomodulatory activity and non-specific suppressor cell generation by spirogermanium in murine and rat models of cell-mediated immunity

Spirogermanium (SG) is a metal-containing compound reported to have antitumor, antiarthritic, antimalarial and immunoregulatory activity. In this study we have demonstrated that treatment of mice and rats with spirogermanium results in an inhibition of autoimmune disease and cell-mediated immune (CMI) responses. Prophylactic administration of SG inhibited the development of adjuvant-induced arthritis and the DTH response to purified protein derivative (PPD) in Lewis strain rats. SG treatment was also able to alleviate the symptoms of experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats. In two strains of mice, BDF1 and C57B1/6, the DTH response to sheep red blood cells could be suppressed by intraperitoneal (i.p.) administration of SG. The spleens of both mice and rats that have been treated with this drug contain suppressor cells which inhibit the response of normal cells to concanavalin A (Con A) and the mixed lymphocyte reaction. In addition, the generation of cytotoxic T cells (CTL) in the murine MLR is abrogated in the presence of these suppressor cells. The suppressor cells were radiation-resistant (2000 rad), indomethacin-insensitive and were not depleted by treatment with anti-Thy-1.2 antiserum plus complement. These results suggest that SG modulates cell-mediated immune responses in vivo by the induction of non-specific suppressor cells.

Suppressor cell induction by the anticancer drug spirogermanium

Spirogermanium is a metal-containing compound reported to have antitumor, antiarthritic, antimalarial and immunoregulatory activity. In this study we have demonstrated that spirogermanium inhibited antibody synthesis to sheep red blood cells in BDF1 mice in vivo. Spleen cells from these treated mice were unable to respond to this antigen in vitro, and suppressed both the antibody response of normal cells to SRBC and the mitogenic response of normal cells to Concanavalin A in co-culture assays. The cells responsible for this suppression did not belong to the T cell lineage since treatment with anti-Thy-1.2 antiserum and complement did not abrogate the suppression. The suppressor cells were found to be radiation resistant and nylon wool adherent. Plastic adherence or passage over Sephadex G10 partially removed the suppression indicating the contribution, at least in part, of a suppressor macrophage. The plastic non-adherent population of cells also contained suppressor cells which were detected following anti-thy-1.2 treatment and selection by panning on anti-IgG coated plates. Fluorescent antibody and flow cytometry technology showed the population of suppressor cells to be 90% immunoglobulin positive, indicative of a B cell lineage.