ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

It has been demonstrated previously that interleukin-1 (IL-1) induces articular cartilage explants and chondrocytes in culture to produce elevated levels of inflammatory mediators such as interleukin-6 (IL-6) and prostaglandins. Previous studies have also demonstrated a relationship between IL-6 secretion and the ability of IL-1 to modulate proteoglycan synthesis by chondrocytes. In this study we have utilized an alginate culture system in an effort to investigate a role for eicosanoids in IL-1 induction of IL-6 expression in human articular chondrocytes. IL-1 treatment of chondrocytes cultured in alginate resulted in increased synthesis of IL-6 and prostaglandins, but not leukotrienes. Cyclo-oxygenase inhibitor, indomethacin (5 μg ml-1), was able to inhibit prostaglandin synthesis to below basal levels with no significant effect on the levels of IL-6 released by chondrocytes in response to IL-1. When chondrocytes were treated with 5 μg ml-1indomethacin and 10 μM of the general lipoxygenase inhibitor, nordihydroguiaretic acid (NDGA), an approximate 50% decrease in IL-1-induced IL-6 expression was observed. Alone, levels of NDGA specific for lipoxygenase inhibition (10 μM) did not affect IL-1-induced IL-6 expression, but higher levels of NDGA (50 μM) which inhibited both prostaglandin and leukotriene biosynthesis reduced IL-1-induced IL-6 expression to the same extent as that observed with 5 μg ml-1indomethacin and 10 μM NDGA. This inhibition of IL-6 expression by NDGA and indomethacin was dose responsive and also reversible with the addition of exogenous prostaglandin E2(PGE2) or leukotriene B4(LTB4). Although IL-1-induced IL-6 expression was only affected when both prostaglandin and leukotriene biosynthesis were inhibited, elevated levels of PGE2but not leukotriene B4, C4, D4, or E4were observed in the culture medium of IL-1-treated chondrocytes. These findings may indicate that cyclo-oxygenase products such as PGE2normally contribute to IL-1 induction of IL-6 expression in chondrocytes, and under conditions when cyclo-oxygenase is inhibited, lipoxygenase products alternatively contribute to this response.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

In recent years, compelling evidence has accumulated that inflammation results from a cascade of events that are orchestrated by cytokines. Cytokines are products of nonimmune and immune cells which regulate the recruitment, differentiation, and proliferation of inflammatory cells. Although there is redundancy in cytokine production and function, major pathways of cytokines have been identified. Besides macrophages, T cells represent important sources of pro- and anti-inflammatory cytokines. In support of a critical regulatory role of T cells in inflammation, two T cell subtypes characterized by different cytokine profiles have been described. TH1 cells produce interleukin-2 (IL-2) and interferon-γ (IFN-γ) and are prone to interact with macrophages. TH2 cells are producers of IL-4, IL-5, and IL-10 and are capable of supporting B cells and eosinophils. Here, we are providing evidence that different human inflammatory diseases are characterized by distinct in situ cytokine patterns. Giant cell vasculitis represents a typical TH1-like disease, whereas TH2 helper cells appear to be more important in rheumatoid arthritis. Given the association of different diseases with cytokine profiles, the question arises how the microenvironment influences cytokine pattern and thus disease and whether mediators produced at the site of inflammation could serve as therapeutic targets to modulate the cytokine cascade. Prostaglandin E2(PGE2) is an important inflammatory mediator. We have examined the influence of PGE2and the PGE analog misoprostol on T-cell function and T-cell cytokine production. Here, we describe that IL-2 and IFN-γ production are sensitive to PGE2and misoprostol, whereas IL-4 and IL-5 are unaffected. Thus, in the presence of PGE2, TH0 cells acquire a TH2-like function, whereas TH1-like aspects are suppressed. We suggest that PGE2and misoprostol might represent useful modulators of the cytokine network.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Endogenous glucocorticoids are of prime importance in the maintenance of cellular homeostasis through their binding to specific cell receptors. Under normal conditions, physiological concentrations of cortisol are potentially capable of suppressing metalloprotease synthesis by chondrocytes and synoviocytes. This hormone action is likely to represent one of the major pathways through which the catabolism of cartilage under physiological conditions is kept in a homeostatic state. In osteoarthritis (OA), a severe reduction (about 50%) in the glucocorticoid receptor (GR) level in chondrocytes was found to be sufficient to alter the cellular steroid resistance in terms of the synthesis of destructive enzymes. Prostaglandins of the E series and dibutyryl cyclic AMP increased the GR level in normal and OA human articular chondrocytes. Synthetic PGE1(misoprostol) also induced upregulation of GR expression in chondrocytes. Naproxen and indomethacin, but not tiaprofenic acid, at therapeutic concentrations, significantly reduced the level of GR in synovial cells. This effect could be reversed by the addition of misoprostol. These findings bring insight into the differential effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on the GR system and may provide an explanation for the reduced level of GR found in OA chondrocytes. The addition of synthetic prostaglandins may prove to be of therapeutic importance in the treatment of arthritic diseases by potentiating the effects of therapeutically administered glucocorticoid on the reduction of the catabolism of articular cartilage.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Prostaglandins are autacoids that elevate intracellular 3':5'-cyclic adenosine monophosphate (cAMP) levels in chondrocytes and other cells in culture. To facilitate intracellular cAMP accumulation, bovine chondrocytes were incubated with forskolin alone or forskolin and isobutylmethylxanthine. Both significantly increased proteoglycan synthesis, which was inhibited by the cAMP-dependent protein kinase inhibitor H89. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) on 3–16% gels revealed the presence of two large proteoglycan core proteins which migrated more slowly than the 200-kDa marker protein and two small proteoglycan core proteins which migrated slightly slower than the 46-kDa marker. Northern blot hybridization, employing32P-labeled cDNA probes, showed that aggrecan steady-state mRNA levels were increased by forskolin and isobutylmethylxanthine after 1 h and 5 h of incubation. Decorin and type II collagen mRNA levels were not altered under these conditions. Link protein mRNA levels were slightly elevated, but only at the 5-h time point. These results indicated that stimulation of intracellular cAMP accumulation by forskolin or forskolin and isobutylmethylxanthine resulted in augmented proteoglycan synthesis via increased steady-state aggrecan mRNA levels. Suppression of proteoglycan synthesis by the cAMP-dependent protein kinase inhibitor H89 suggested that cAMP-dependent protein kinase may also play a role in regulating the synthesis and completion of newly synthesized proteoglycans.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Prostaglandins are potent stimulators of bone resorption and formation. Because misoprostol is an analog of prostaglandin E1(PGE1), we have examined its effects on resorption and formation in organ culture. The results were compared with PGE2which can stimulate resorption and both stimulate and inhibit bone formation. Resorption, measured as the release of previously incorporated45Ca from 5-day cultures of 19-day fetal-rat long bones, was increased by misoprostol 1.5-fold at 10-6M and twofold at 10-5M. The effect at 10-6M was abolished by addition of indomethacin (10-6M). PGE2was approximately 100 times more potent and was not affected by indomethacin in this system. In 21-day fetal-rat calvariae, cultured for 24 h in the presence of cortisol (10-7M), misoprostol produced a dose-related increase in TdR incorporation between 10-5and 10-7M. PGE2appeared to be only 10-fold more potent in this response. The effects of misoprostol on incorporation of [3H]proline into collagenase digestible protein (CDP) and noncollagen protein (NCP) were measured in 72-h cultures, either with continuous treatment or 24-h treatment followed by 48 h in control medium. With continuous treatment at 10-6M, misoprostol increased labeling of CDP twofold. A similar effect was observed with 24 h of treatment at 10-5M, followed by 48 h in control medium. Again, PGE2was approximately 10-fold more potent than misoprostol. When calvariae were treated with insulin-like growth factor I, which increases CDP labeling by 2.5-fold, the effects of misoprostol and PGE2were inhibitory. We conclude that misoprostol resembles PGE2in its effects on bone but is less potent. Moreover, misoprostol may be relatively less effective in stimulating resorption than in stimulating formation. Therefore, an increase in bone turnover, possibly with a net anabolic effect, might occurin vivowith long-term misoprostol treatment. Misoprostol effects on bone turnover in humans could be evaluated using the sensitive biochemical markers for bone resorption and formation which are currently available.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The zone of calcified cartilage (ZCC) which provides the critical interface between cartilage and bone acts as the growth plate in the developing joint. In osteoarthritis, it has been hypothesized that the ZCC may again function in joint remodeling. This could result in thinning of the cartilage. This report is the first experimental confirmation of this hypothesis.Osteoarthritis was induced using the Hulth procedure in 2.3–2.7-kg rabbits. Approximately 3 weeks after surgery, half of the menisectomy rabbits and half of the nonmenisectomy rabbits were given 20 μg of misoprostol interarticularly for 5 days per week for 2.5 weeks. In the patellae and tibial plateau, the rate of movement of the tidemark of the ZCC was measured. Medial aspect femoral condyle cartilage was incubated in the presence of [35S]sulfate and [3H]proline. After menisectomy, rate of movement of the ZCC was dramatically increased and was unchanged by misoprostol. Proteoglycan synthesis was highly elevated in the osteoarthritis-induced knees, and misoprostol suppressed the rate of [35S]sulfate but not [3H]proline incorporation.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The cytochromes P450 comprise a superfamily of mixed function oxidases responsible for the oxidation of numerous endobiotics and thousands of xenobiotics. Though they are distributed in many organ systems, the hepatic cytochromes P450 are most prominent in both the detoxification and bioactivation of xenobiotics. They have been investigated intensively for over 30 years; however a systematic nomenclature did not evolve until it became clear that numerous isoforms existed. Based on similarities of amino acid sequences, the cytochrome P450 (CYP) enzymes have now been classified by family, subfamily, and isoform. As expression systems have been developed to assist in the determination of which isoforms mediate the oxidations of which substrates, it has become possible to model binding sites for some of the isoforms. This enterprise has been assisted by the determination of the amino acid sequence and the X-ray crystal structure of the bacterial cytochrome P450, P450CAM.As the CYP enzymes play such a vital role in drug metabolism, and as the activities of various CYP isoforms have been implicated in cancer risk, there is a compelling need to develop methods for genotyping or phenotyping subpopulations with regard to CYP activity. It should be especially important to phenotype CYP activities in subpopulations anytime CYP enzyme activity can be regulated by environmental factors. A priori knowledge about CYP activity in various subpopulations (e.g., the aged, those with hepatic dysfunction, women, those occupationally exposed to certain environmental chemicals) will be helpful in predicting therapeutic outcomes for drugs whose elimination is CYP dependent. Additionally, cancer risk has been shown to correlate with various CYP activities, suggesting that a priori knowledge about select CYP activities may be useful in cancer risk assessment.Several noninvasive and minimally invasive strategies for phenotyping CYP activities have emerged in recent years. These procedures hold the promise of permitting investigators to phenotype select CYP isoform or subfamily activities within defined subpopulations through the use of endobiotic probes of CYP activity, xenobiotic probes of CYP activity, and noninvasive and minimally invasive measurements of those probes. This article reviews the CYP enzymes, the minimally invasive and noninvasive methods for characterizing their hepatic activities in humansin vivo, and the significance of being able to phenotype their activitiesin vivo.

ISSN:1075-2765    

出版商:OVID    

年代:1996

数据来源: OVID