Prostaglandins in pathological bone resorption

Role of Macrophage Migration Inhibitory Factor in Paranasal Sinus Mucocele

Background

Little is known about the immunologic aspects and the pathogenesis of the paranasal sinus mucocele.

Methods

The fluids of paranasal sinus mucoceles were obtained from 12 subjects. The concentration of macrophage migration inhibitory factor (MIF), interleukin 1β, tumor necrosis factor a, and regulated on activation normal T cell expressed and secreted (RANTES) were determined by enzyme-linked immunosorbent assay, and the levels of endotoxin were detected with kinetic Turbidimetric Assay.

Results

MIF and endotoxin were detected in the fluid of all samples, whereas interleukin-1β and RANTES were detected in 1 and 3 subjects out of 12 samples. Tumor necrosis factor a was not detected in any of the samples. A significant positive correlation between the levels of MIF and the period with symptoms such as pain, swelling of face, and visual disturbance was observed.

Conclusion

These findings suggest that MIF and endotoxin may play an important role in the pathogenesis of paranasal sinus mucocele. MIF may be an important factor causing the development and exacerbation of the disease.

Expression of IL-12 and T helper cell 1 cytokines in the fluid of paranasal sinus mucoceles

OBJECTIVE

The objective of this study was to assess the expression of regulatory cytokines and T helper cell (Th)1/Th2 cytokines in paranasal sinus mucoceles.

MATERIALS AND METHODS

Fluid samples of 12 paranasal sinus mucoceles were assessed by enzyme-linked immunosorbent assay for concentrations of regulatory cytokines (interleukin [IL]-10 and IL-12), Th1 cytokines (IL-2 and interferon gamma), and Th2 cytokines (IL-4 and IL-5).

RESULTS

IL-12 was detected in all samples, whereas IL-10 was detected in only one case. The concentration of IL-12 tended to correlate with that of interferon gamma and was significantly and positively correlated with that of IL-2.

CONCLUSIONS

Th1 cytokines and the Th1 regulatory cytokine IL-12, but not IL-10, potentially play a key role in the pathogenesis of paranasal sinus mucoceles. Together with our recent report showing that lipopolysaccharide is highly detected in mucocele fluid, the data from this study suggest that the Th1 response induced by lipopolysaccharide may affect the immunological inflammation in the epithelium of paranasal sinus mucoceles.

Fibrous tissue of subchondral cystic lesions in horses produce local mediators and neutral metalloproteinases and cause bone resorption in vitro

OBJECTIVES

To define the release of nitric oxide (NO), prostaglandin E2 (PGE2), and the neutral metalloproteinases (NMPs) in horses with subchondral cystic lesions (SCL) and to study bone resorption triggered by conditioned media of fibrous tissue of SCL in vitro.

STUDY DESIGN

Equine explant cultures of fibrous tissue of SCL, and synovial membrane and articular cartilage of normal horses and horses affected with moderate and severe osteoarthritis were performed. NO, PGE2, and NMP concentrations of media samples were measured, and osteoclast formation and activation was studied in vitro.

ANIMALS

Experiment 1: 32 horses with SCL (n = 8), normal joints (7), and joints with moderate (7) and severe (10) osteoarthritis (OA). Experiment 2: 22 horses with SCL (n = 3), normal joints (7), and chip fractures (12). Experiment 3: Conditioned media of fibrous tissue from 3 horses with SCL of the medial femoral condyle (n = 1), distal metacarpal bone (1), and tarsal bone (1).

METHODS

Determinations of local mediator concentrations were made with the Griess assay for NO and an enzyme immunoassay kit for PGE2 concentrations in biological fluids. Enzyme activities were assessed with radiolabeled substrates indicating collagenolytic, gelatinolytic, and caseinolytic activities. The resorption pit assay was used to assess osteoclast recruitment and activity.

RESULTS

Fibrous tissue of SCL produced NO, PGE2, and NMPs. Of all the variables measured, PGE2 concentrations were the highest in cystic tissue of SCL compared with synovial membrane and articular cartilage from normal joints and joints with chip fractures, indicating that this mediator may play an important role in pathological bone resorption associated with SCL. These findings were supported by the observation that conditioned media of SCL tissue were capable of recruiting osteoclasts and increasing their activity.

CONCLUSION

Fibrous tissue of SCL released NO, PGE2, and NMPs into the culture media. It is suspected that intralesional fibrous tissue may play an active role in the pathological process of bone resorption occurring in SCL in horses and may be partly responsible for the maintenance, slow healing rate, and expansion of these lesions.

CLINICAL RELEVANCE

Understanding the pathogenesis of SCL will help to establish successful therapy in horses affected with SCL.

Involvement of cytokines and vascular adhesion receptors in the pathology of fronto-ethmoidal mucocoeles

Fronto-ethmoidal mucocoeles have the capacity to destroy bone. Sinus lining tissue has been obtained at surgery from patients with mucocoeles, from those with chronic sinusitis undergoing endoscopic sinus surgery and from patients undergoing craniofacial resection. Tissues have been frozen, sectioned, and subjected to immunohistochemical examination with monospecific antibodies for the presence of the potent osteolytic cytokines interleukins-1 and -6 and tumour necrosis factor alpha. In addition, the chemotactic intercrine--interleukin-8 was investigated. The presence of the cytokine-inducible vascular endothelial adhesion receptors--Inter-Cellular Adhesion Molecule (ICAM)-1 and E-Selectin (also known as Endothelial Leukocyte Adhesion Molecule--ELAM) was also determined. Normal sinus tissue showed no immunoreactivity with the antibodies to these various moieties. Surprisingly, only a small proportion of tissues from patients with chronic sinusitis showed the presence of cytokines or vascular adhesion receptors. In contrast, all specimens of fronto-ethmoidal mucocoeles showed positive staining for IL-1 alpha and beta and for ICAM-1 and E-selectin. IL-1 immunostaining was restricted to the epithelial cell population not being found in infiltrating leukocytes. In 40% of mucocoeles infiltrating macrophage-like cells showed the presence of tumour necrosis factor alpha. The presence of the potent osteolytic cytokine--IL-1 in all specimens of fronto-ethmoidal mucocoeles coupled to the finding of the IL-1-inducible adhesion molecules ICAM-1 and E-Selectin argues strongly that IL-1 is released from the epithelial cells and that this cytokine may be the factor causing the erosion of bone overlying the expanding mucocoele. The nature of the signals inducing cytokine synthesis remain, however, unidentified.

Intraosseous infusion of prostaglandin E2 in the caprine tibia

We evaluated the effects of intraosseously administered prostaglandin E2 (PGE2) within the proximal metaphysis of the goat (caprine) tibia under intraosseous normotensive and hypertensive conditions. PGE2 was administered at 0.5 or 1.0 mg (1 ml vol) twice daily for 10 days via an Osteoport which had been surgically implanted within the proximal tibial metaphysis. Intraosseous hypertension was produced when venous outflow obstruction (VOO) was created by ligation of the popliteal vein, which drained the proximal tibia, and occlusion of the diaphyseal medullary space distally with bone cement. After VOO, the intraosseous pressure measured at the metaphysis increased significantly (p < 0.05) from a baseline mean of 14.9 +/- 4.2 mm Hg to 28.6 +/- 5.3 mm Hg. Serum radioimmunoassays indicated that VOO prolonged the venous drainage of PGE2 from the tibia after an infusion. Static histomorphometric analysis indicated a marked dose-dependent increase in new bone formation in all PGE2 groups at 30 days after the PGE2 infusion. Significant (p < 0.05) formation of new bone occurred, primarily at the subperiosteal and endocortical surfaces, and moderately increased the marrow cavity of cancellous new bone as compared with the VOO-only group and the controls. Bone remodeling indices were also increased by PGE2. The PGE2 infusion, combined with VOO, produced significantly more new bone formation than the PGE2 infusion alone. Intensive marrow fibrosis was associated with the active bone remodeling.

Biologic properties of eugenol and zinc oxide-eugenol. A clinically oriented review

Eugenol-containing dental materials are frequently used in clinical dentistry. When zinc oxide-eugenol (ZOE) is applied to a dentinal cavity, small quantities of eugenol diffuse through the dentin to the pulp. Low concentrations of eugenol exert anti-inflammatory and local anesthetic effects on the dental pulp. Thus use of ZOE temporary filling may facilitate pulpal healing; on the other hand, high eugenol concentrations are cytotoxic. Direct application of eugenol to pulp tissue may result in extensive tissue damage. The ability of ZOE-based endodontic sealers to influence periapical tissue healing is considered in view of eugenol's anti-inflammatory and toxic properties.

Interleukin-one induced arachidonic acid turnover in macrophages

Recombinant Interleukin-1 beta (rIL-1 beta) induced dose-dependent synthesis of PGE2 and activation of both cell-associated and soluble phospholipase A2 (PLA2) in cultured mouse peritoneal macrophages. Kinetic studies showed that rIL-1 beta was able to induce a 2-fold increase in membrane bound PLA2 activity in the cells within 1 hour. Elevated levels of PGE2 were however observed only after 4 hours stimulation of the cells while significant levels of soluble PLA2 activity were observed only after 16 hours stimulation of the cells. Stimulation with rIL-1 beta of macrophage cultures pre-labelled with [14C]arachidonic acid resulted in a loss of label from both phosphatidyl-choline and phosphatidylinositol in only 10 min, which was not observed in control (unstimulated) cultures. These results are indicative that the two phospholipids are the principal source of arachidonic acid for IL-1 induced prostaglandin synthesis.

Fatty acid cyclooxygenase activity stimulated by transforming growth factor-beta in mouse osteoblastic cells (MC3T3-E1)

Prostaglandin (PG)E2, a bone-resorption factor, was released essentially as the sole arachidonate metabolite by an osteogenic cell line cloned from mouse calvaria (MC3T3-E1). Transforming growth factor (TGF)-beta (1 ng/ml) or epidermal growth factor (EGF) (10 ng/ml) markedly stimulated the endogenous PGE2 synthesis in the presence of 5% newborn bovine serum. The serum could not be omitted even if both TGF-beta and EGF were added simultaneously. The PGE2 synthesis started after a 1-h lag phase, and reached a maximum at about 3 h after the addition of TGF-beta. The presence of TGF-beta enhanced the cyclooxygenase activity (arachidonic acid----PGH2) assayed with the microsomes or the immunoprecipitate from the solubilized enzyme. The TGF-beta-stimulated PGE2 synthesis was blocked by translation and transcription inhibitors. Furthermore, Western blot analysis using anti-cyclooxygenase antibody demonstrated a higher level of cyclooxygenase in the TGF-beta-treated cells than in the nontreated cells. These experimental results suggested an induction of cyclooxygenase by TGF-beta as previously reported for EGF (K. Yokota et al. (1986) J. Biol. Chem. 261, 15,410-15,415).

Effects of diclofenac, indomethacin, tolfenamic acid and hydrocortisone on prostanoid production in healthy and rheumatic synovial cells

Prostanoids, found in enhanced concentrations in rheumatic synovial fluid, are involved in the joint destruction seen in rheumatoid arthritis. Adherent cells isolated from rheumatic synovia produce higher amounts of prostanoids in a primary cell culture than cells originating from non-inflamed synovia. In the present study, it was found that exogenous arachidonic acid diminished the differences in prostanoid production between healthy and rheumatic synovial cells. Non-steroidal anti-inflammatory analgesics in clinically relevant concentrations had similar inhibitory effects on arachidonic acid-stimulated prostanoid synthesis in both healthy and rheumatic cells. In the presence of exogenous arachidonic acid, hydrocortisone (0.3-5.0 microM) did not affect prostanoid production in healthy cells. In rheumatic synovial cells hydrocortisone reduced PGE2 and PGF2 alpha synthesis to about half of the control value and the effect was not reversed by adding excess exogenous arachidonic acid. Altered regulation of phospholipase A2 activity in rheumatic synovia could explain the observed differences between healthy and rheumatic synovial cells.

Possible induction of fatty acid cyclooxygenase in mouse osteoblastic cells (MC3T3-E1) by cAMP

Prostaglandin E2 (PGE2), a bone-resorption factor, was essentially the sole arachidonate metabolite in an osteoblastic cell line cloned from mouse calvaria (MC3T3-E1). When the cells were cultured in the presence of 2% newborn bovine serum, 1 microM epinephrine markedly stimulated PGE2 synthesis from endogenous arachidonic acid. The PGE2 synthesis commenced after a lag phase of 1-2 h, and reached a maximum at about 3 h after the addition of epinephrine. The effect of epinephrine was inhibited by propranolol, and epinephrine could be replaced by isoproterenol, suggesting beta-adrenergic stimulation of PGE2 production. A rapid increase in intracellular cAMP was observed upon the addition of epinephrine. When the intracellular cAMP level was raised using cholera toxin or forskolin, the PGE2 synthesis was also stimulated. The enhanced PGE2 synthesis was attributed to an increased level of cyclooxygenase, which was shown by immunoprecipitation of the enzyme using anti-cyclooxygenase antibody. Inhibitors of transcription and translation suppressed the epinephrine-dependent increase in cyclooxygenase activity. These findings suggest induction of cyclooxygenase involving cAMP via an as yet unclarified mechanism.

Role of prostaglandins in bone resorption in a synchronized remodeling sequence in the rat

The role of prostaglandins (PGs) in physiological remodeling has not yet been defined. The present study was undertaken to determine whether they intervene during the activation phase in a highly reproducible and synchronized model of bone remodeling. Indomethacin was employed to inhibit PG synthesis. This treatment throughout the entire activation period (4 days in this model) inhibited osteoclastic resorption completely. By modifying the treatment procedure, it appeared that PGs were operative mainly between the second and third day of activation. PGs did not seem to act on precursor recruitment, since off-bone osteoclasts (putatively inactive cells) were numerous in the treated groups. PGs might also be involved in osteoclast activity as the mean interface between osteoclasts and bone surface was reduced in the treated groups. However, indomethacin was unable to inhibit the remodeling sequence durably since a 6-day treatment resulted in a high profile of resorption. This suggests that factors other than PGs were responsible for activating resorption.