A genome scan localizes five non-MHC loci controlling collagen-induced arthritis in rats.

Identification of specific genetic loci that contribute to susceptibility to rheumatoid arthritis (RA) in humans has been hampered by several factors, including: i) multiple interacting genetic loci contributing to susceptibility; ii) complex interactions of environmental and genetic factors; iii) genetic heterogeneity; and iv) low penetrance. We have, therefore, mapped quantitative trait loci (QTLs) that control inflammatory arthritis susceptibility and/or severity in progeny of two inbred rat strains with significantly different susceptibilities to collagen-induced arthritis (CIA), an animal model for RA. Not surprisingly, we identified a major susceptibility factor, Cia1, on chromosome 20 in the vicinity of the rat major histocompatibility complex (MHC). However, by limiting the analysis to animals with arthritis-susceptible MHC genotypes and using genome-wide QTL analytic techniques, we also found four non-MHC QTLs-Cia2, 3, 4 and 5-on chromosomes 1, 4, 7 and 10, that contributed to disease severity. In addition, a QTL on chromosome 8 was suggestive for linkage. Characterization of the genes underlying these QTLs will facilitate the identification of key biochemical pathways regulating experimental autoimmune arthritis in rats and may provide insights into RA and other human autoimmune diseases. These genes may also represent novel targets for therapy.

Monoreactive high affinity and polyreactive low affinity rheumatoid factors are produced by CD5+ B cells from patients with rheumatoid arthritis.

In patients with rheumatoid arthritis (RA), circulating CD5+ B lymphocytes, but not CD5- B lymphocytes, are increased in number and size, exist in an activated state, spontaneously proliferate, and secrete Ig that binds to the Fc fragment of IgG. By constructing continuous mAb-secreting cell lines from CD5+ B lymphocytes, the properties and dissociation constants (Kd) of these antibodies were determined. Two types of rheumatoid factors (RFs) with discrete reactivities were produced. The first type is polyreactive and binds with relatively low affinity (Kd, 10(-5) mol/liter) to the Fc fragment of IgG. These antibodies are similar to those produced by CD5+ B cells from healthy subjects. The second type of RF is monoreactive and binds with higher affinity (Kd, 10(-7) mol/liter) to the Fc fragment of IgG. These latter autoantibodies are produced by CD5+ B cells of RA patients, but not healthy subjects. Long-term longitudinal studies are needed to determine the role of these two types of RFs in the pathogenesis of RA.

Spontaneous production of fibroblast-activating factor(s) by synovial inflammatory cells. A potential mechanism for enhanced tissue destruction.

A characteristic feature of rheumatoid arthritis is hyperplasia of the synovial lining cells and fibroblasts, the source of tissue-degrading mediators, in association with the appearance and persistence of lymphocytes in affected joints. Diseased synovial tissue obtained at arthroscopy from 10 of 12 rheumatoid arthritis patients was found to release a factor(s) that could stimulate quiescent fibroblasts to proliferate in vitro. Mononuclear cells isolated from this synovial tissue and from the synovial fluid spontaneously produced fibroblast-activating factor(s) (FAF). In contrast, synovial tissue from patients with noninflammatory joint disease did not release FAF. By gel filtration, FAF was detected in two peaks (40,000 and 15,000 mol wt) that were consistent with the previously described peripheral blood T lymphocyte- and monocyte-derived factors with identical activity. The mononuclear cells were predominantly OKT3+/Leu-1+ T lymphocytes and OKM1+ cells of monocyte/macrophage lineage that expressed HLA-DR antigens, suggesting prior activation of these cells. Mononuclear cells isolated from the peripheral blood of these patients did not spontaneously secrete FAF. Lymphocytes and monocytes from the site of synovial inflammation appear to be activated in situ to produce factors that may contribute to the hyperplasia and overgrowth of the synovial membrane in rheumatoid arthritis.

Bacterial cell wall-induced hepatic granulomas. An in vivo model of T cell-dependent fibrosis.

In vitro studies implicate a molecular link between inflammatory mononuclear cells and alterations in fibroblast growth and function. We have extended these observations in an experimental animal model in which we document the T cell-dependence of fibrosis that occurs after activation of the cell-mediated immune system by specific antigen. Chronic granulomatous lesions were induced in the livers of susceptible rats by the intraperitoneal injection of group A streptococcal cell walls (SCW). The development of granulomas that are composed primarily of lymphocytes and macrophages was associated with the recruitment and proliferation of connective tissue cells. Furthermore, this expanded population of fibroblasts generated a collagenous structure consisting primarily of types I and III collagen around the granuloma. The progression of these chronic inflammatory lesions leads to the formation of fibrotic nodules throughout the livers of the treated animals. Intact granulomas, as well as mononuclear cells derived from the granulomas, spontaneously elaborated a soluble factor(s) that stimulates fibroblast proliferation. Physicochemical analysis revealed that the primary granuloma-derived peak of fibroblast growth activity corresponded to an apparent Mr of 40,000, which is consistent with a previously described T lymphocyte--derived fibroblast-activating factor (FAF) in guinea pig and human. Furthermore, the fibrosis that occurs in the granuloma is apparently T cell--dependent, since no fibrotic lesions developed in SCW-injected athymic nude rats nor in SCW-injected animals treated with the T cell inhibitor, cyclosporin A (CsA). Mononuclear cells from neither of these functionally T cell--deficient animals could generate FAF activity. These data show a role for T lymphocyte--derived cytokines in the development of hepatic fibrosis in SCW-injected rats.

Detection of high levels of heparin binding growth factor-1 (acidic fibroblast growth factor) in inflammatory arthritic joints.

The synovium from patients with rheumatoid arthritis (RA) and LEW/N rats with streptococcal cell wall (SCW) arthritis, an experimental model resembling RA, is characterized by massive proliferation of synovial connective tissues and invasive destruction of periarticular bone and cartilage. Since heparin binding growth factor (HBGF)-1, the precursor of acidic fibroblast growth factor (FGF), is a potent angiogenic polypeptide and mitogen for mesenchymal cells, we sought evidence that it was involved in the synovial pathology of RA and SCW arthritis. HBGF-1 mRNA was detected in RA synovium using the polymerase chain reaction technique, and its product was immunolocalized intracellularly in both RA and osteoarthritis (OA) synovium. HBGF-1 staining was more extensive and intense in synovium of RA patients than OA and correlated with the extent and intensity of synovial mononuclear cell infiltration. HBGF-1 staining also correlated with c-Fos protein staining. In SCW arthritis, HBGF-1 immunostaining was noted in bone marrow, bone, cartilage, synovium, ligamentous and tendinous structures, as well as various dermal structures and developed early in both T-cell competent and incompetent rats. Persistent high level immunostaining of HBGF-1 was only noted in T-cell competent rats like the disease process in general. These observations implicate HBGF-1 in a multitude of biological functions in inflammatory joint diseases.

The role of intuition.

"Intuition," as used by the modern mathematician, means an accumulation of attitudes (including beliefs and opinions) derived from experience, both individual and cultural. It is closely associated with mathematical knowledge, which forms the basis of intuition. This knowledge contributes to the growth of intuition and is in turn increased by new conceptual materials suggested by intuition. The major role of intuition is to provide a conceptual foundation that suggests the directions which new research should take. The opinion of the individual mathematician regarding existence of mathematical concepts (number, geometric notions, and the like) are provided by this intuition; these opinions are frequently so firmly held as to merit the appellation "Platonic." The role of intuition in research is to provide the "educated guess," which may prove to be true or false; but in either case, progress cannot be made without it and even a false guess may lead to progress. Thus intuition also plays a major role in the evolution of mathematical concepts. The advance of mathematical knowledge periodically reveals flaws in cultural intuition; these result in "crises," the solution of which result in a more mature intuition. The ultimate basis of modern mathematics is thus mathematical intuition. and it is in this sense that the Intuitionistic doctrine of Brouwer and his followers is correct. Modern instructional methods recognize this role of intuition by replacing the "do this, do that" mode of teaching by a "what should be done next?" attitude which appeals to the intuitive background already developed. It is in this way that understanding and appreciation of new mathematical knowledge may be properly instilled in the student.

Autocrine or paracrine inflammatory actions of corticotropin-releasing hormone in vivo.

Corticotropin-releasing hormone (CRH) functions as a regulator of the hypothalamic-pituitary-adrenal axis and coordinator of the stress response. CRH receptors exist in peripheral sites of the immune system, and CRH promotes several immune functions in vitro. The effect of systemic immunoneutralization of CRH was tested in an experimental model of chemically induced aseptic inflammation in rats. Intraperitoneal administration of rabbit antiserum to CRH caused suppression of both inflammatory exudate volume and cell concentration by approximately 50 to 60 percent. CRH was detected in the inflamed area but not in the systemic circulation. Immunoreactive CRH is therefore produced in peripheral inflammatory sites where, in contrast to its systemic indirect immunosuppressive effects, it acts as an autocrine or paracrine inflammatory cytokine.

Thymus-dependent and -independent regulation of Ia antigen expression in situ by cells in the synovium of rats with streptococcal cell wall-induced arthritis. Differences in site and intensity of expression in euthymic, athymic, and cyclosporin A-treated LEW and F344 rats.

Euthymic LEW rats, when injected with streptococcal cell walls, exhibited rapid onset development of acute exudative arthritis coincident with enhanced synovial expression of Ia antigen. By 21 d after injection, the expression of Ia was markedly increased compared with basal conditions and paralleled the severity of the later developing proliferative and erosive disease. Immunodeficient athymic and cyclosporin A-treated LEW rats developed only the early phase arthritis, which was again paralleled by synovial Ia expression. Chronic expression of high levels of Ia antigen was not observed. Histocompatible F344 rats, both athymic and euthymic, developed minimal, if any, clinically significant arthritis and did not exhibit the enhanced Ia expression demonstrated in the LEW rats. Our results indicate that enhanced synovial Ia expression parallels clinical disease severity and varies by rat strain, and that the rapid onset enhanced synovial Ia expression is thymus independent, whereas the markedly enhanced chronic phase Ia expression is thymus dependent.

Local secretion of corticotropin-releasing hormone in the joints of Lewis rats with inflammatory arthritis.

Corticotropin-releasing hormone (CRH), the principal regulator of the hypothalamic-pituitary-adrenal axis, is also secreted in peripheral inflammatory sites, where it acts as a local proinflammatory agent. Arthritis-susceptible LEW/N rats have profoundly deficient hypothalamic CRH responses to inflammatory stimuli and other stressors. Arthritis-resistant F344/N rats, on the other hand, have a robust increase in hypothalamic CRH in response to the same stimuli. Contrasting with these hypothalamic CRH responses, we now show that CRH expression is markedly increased in the joints and surrounding tissues of LEW/N rats with streptococcal cell wall- and adjuvant-induced arthritis, whereas it is not increased in similarly treated F344/N rats and is only transiently increased in congenitally athymic nude LEW.rnu/rnu rats. Glucocorticoid treatment suppressed, but did not eliminate, CRH immunoreactivity in the joints of LEW/N rats. CRH mRNA was present in inflamed synovia, as well as in spinal cord, and inflamed synovia also expressed specific CRH-binding sites. We compared CRH expression in inflamed joints with another well-characterized proinflammatory neuropeptide, substance P (SP), and found that SP immunoreactivity paralleled that of CRH. In summary, although LEW/N rats have deficient hypothalamic CRH responses to inflammatory stimuli compared with F344/N rats, they express relatively high levels of CRH at the site of inflammation. Analogous to SP, CRH may be delivered to the inflammatory site by peripheral nerves and/or synthesized at the inflammatory site. These data provide further support for the concept that CRH not only triggers the pituitary-adrenal antiinflammatory cascade, but also functions as an antithetically active local mediator of acute and chronic inflammatory arthritis. These data also illustrate the complex interrelationships of the nervous, endocrine, immune, and inflammatory systems.

In vivo cyclooxygenase expression in synovial tissues of patients with rheumatoid arthritis and osteoarthritis and rats with adjuvant and streptococcal cell wall arthritis.

Cyclooxygenase (COX), or prostaglandin (PG) H synthase, plays a role in inflammatory diseases, but very limited data exist on the regulation of COX in vivo. We, therefore, studied the in vivo expression of COX in synovia from patients with rheumatoid arthritis (RA) and osteoarthritis (OA), as well as joints of rats with streptococcal cell wall (SCW) and adjuvant arthritis. Extensive and intense intracellular COX immunostaining, which correlated with the extent and intensity of mononuclear cell infiltration, was observed in cells throughout RA synovia. Significantly less or equivocal staining was noted in OA and normal human synovia. Similarly, COX immunostaining was equivocal in the joints of normal and arthritis-resistant F344/N rats. In contrast, high level expression developed rapidly in euthymic female Lewis (LEW/N) rats throughout the hindlimb joints and overlying tissues including skin, preceding or paralleling clinically apparent experimental arthritis. COX was expressed in the joints of athymic LEW.rnu/rnu rats 2-4 d after injection of SCW or adjuvant but was not sustained. Physiological doses of antiinflammatory glucocorticoids, but not progesterone, suppressed both arthritis and COX expression in LEW/N rats. These observations suggest that, in vivo, (a) COX expression is upregulated in inflammatory joint diseases, (b) the level of expression is genetically controlled and is a biochemical correlate of disease severity, (c) sustained high level up-regulation is T cell dependent, and (d) expression is down-regulated by antiinflammatory glucocorticoids.

Immune function in severe, active rheumatoid arthritis. A relationship between peripheral blood mononuclear cell proliferation to soluble antigens and synovial tissue immunohistologic characteristics.

The immunohistology of synovium from a tender, swollen knee and peripheral blood cellular immune function were correlated in 24 clinically similar patients with active, seropositive rheumatoid arthritis who were not taking cytotoxic or long-acting antirheumatic drugs. The patients were classified as anergic (n = 6) or nonanergic (n = 18) on the basis of peripheral blood mononuclear cell proliferative responses to a battery of soluble recall antigens. The peripheral blood mononuclear cells of anergic patients failed to respond significantly to any soluble recall antigen, whereas cells from nonanergic patients responded to at least one such antigen. Multiple pieces of synovial tissue were obtained from each patient at arthroscopy. To minimize intrajoint variability, all pieces were analyzed and averaged to determine a composite profile of abnormalities. Synovial specimens from all six anergic patients had "high intensity" lymphocytic infiltration (group A). In sharp contrast, synovial specimens from 15 of 18 nonanergic patients had "low intensity" lymphocytic infiltration (group B) (P = 0.002). Group A tissues typically showed higher intensity T cell and plasma cell infiltration, more synovial lining layer hyperplasia, more HLA-DR bearing cells, and a higher ratio of Leu 3A/Leu 2A T cells than did group B. Group B tissues had fewer infiltrating cells (most of which were OKM1 and HLA-DR bearing), more extensive fibrin deposition, and far fewer T and plasma cells. Although these data do not imply that synovium from different joints in an individual patient are immunohistologically identical, they do provide evidence that peripheral blood mononuclear cell immune function reflects immunopathologic events in the biopsied joint. Moreover, the data further support the view that clinically active rheumatoid arthritis is, like certain other chronic inflammatory conditions, a heterogeneous disorder with polar subgroups.

Role of the thymus in streptococcal cell wall-induced arthritis and hepatic granuloma formation. Comparative studies of pathology and cell wall distribution in athymic and euthymic rats.

Systemic administration of an aqueous suspension of group A streptococcal cell wall fragments to susceptible rats induces acute and chronic polyarthritis, as well as noncaseating hepatic granulomas. To gain insight into the role of the thymus in the pathogenesis of this experimental model, pathologic responses and cell wall tissue distribution were compared in congenitally athymic rats (rnu/rnu) and their euthymic littermates (NIH/rnu). Within 24 h, both rat strains developed acute arthritis, characterized by polymorphonuclear leukocytic exudate in the synovium and joint spaces. This acute process was maximal at day 3 and gradually subsided. Beginning 2-3 wk after injection, the euthymic, but not the athymic, rats developed the typical exacerbation of arthritis, characterized by synovial cell hyperplasia with villus formation and T helper/inducer lymphocyte-rich mononuclear cell infiltration. This process eventually resulted in marginal erosions and destruction of periarticular bone and cartilage. Parallel development of acute and chronic hepatic lesions was observed. Bacterial cell wall antigen distribution and persistence were similar in the athymic and euthymic rats. Cell wall antigens were demonstrated in the cytoplasm of cells within subchondral bone marrow, synovium, liver, and spleen, coincident with the development of the acute lesions, and persisted in these sites, although in decreasing amounts, for the duration of the experiment. Our findings provide evidence that the acute and chronic phases of the experimental model are mechanistically distinct. The thymus and functional thymus derived-lymphocytes appear not to be required for the development of the acute exudative disease but are essential for the development of chronic proliferative and erosive disease. Induction of disease is dependent upon cell wall dissemination to and persistence in the affected tissues.

Transin/stromelysin expression in the synovium of rats with experimental erosive arthritis. In situ localization and kinetics of expression of the transformation-associated metalloproteinase in euthymic and athymic Lewis rats.

Transin is a neutral metalloproteinase initially isolated from malignantly transformed rat fibroblasts and subsequently shown to be homologous to human stromelysin. We performed Northern blot analysis on synovial tissue specimens from Lewis rats with proliferative and invasive streptococcal cell wall (SCW) arthritis. Transin mRNA was present in abundance, as was the mRNA of the c-myc oncogene, which is associated with cellular proliferation. Immunohistochemical staining of synovia from rats with chronic SCW arthritis showed high-level transin expression in the cells of the lining layer and underlying stroma, as well as in chondrocytes and osteoclasts in subchondral bone. Intense nuclear staining for the Myc oncoprotein was also detected with a cross-reactive antibody to v-Myc. Transin stained similarly in the early, rapid-onset, thymus-independent, acute phase of SCW arthritis. In the T cell-dependent adjuvant arthritis, transin expression was noted by day 4, 6 d before the influx of mononuclear cells and the onset of clinical disease. Athymic rats did not express transin. We concluded that transin is a marker of proliferative, invasive arthritis in rats and appears early in the course of disease development, but requires a competent immune system to sustain its expression in these model arthropathies.

Anchorage-independent growth of synoviocytes from arthritic and normal joints. Stimulation by exogenous platelet-derived growth factor and inhibition by transforming growth factor-beta and retinoids.

Exuberant tumor-like synovial cell proliferation with invasion of periarticular bone is a feature of rheumatoid arthritis in humans and of streptococcal cell wall (SCW)-induced arthritis in rats. These histologic observations prompted us to examine synoviocytes from arthritic joints for phenotypic characteristics of transformed cells. The capacity to grow in vitro under anchorage-independent conditions is a characteristic that correlates closely with potential in vivo tumorigenicity. In medium supplemented with 20% serum or in basal media supplemented with platelet-derived growth factor (PDGF), early passage synoviocytes from both SCW-induced and rheumatoid arthritic joints formed colonies in soft agarose. Epidermal growth factor (EGF), interleukin 1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and transforming growth factor-beta (TGF-beta) did not support growth, although EGF enhanced PDGF-dependent growth. On the other hand, TGF-beta, as well as all-trans-retinoic acid, inhibited colony growth. Early passage normal rat and human synoviocytes also grew under the same conditions, but lung, skin, and late-gestation embryonic fibroblast-like cells did not. Considered in the context of other published data our findings provide cogent evidence that synoviocytes, but not other types of fibroblast-like cells, readily acquire phenotypic characteristics commonly associated with transformed cells. Expression of the transformed phenotype in the inflammatory site is likely regulated by paracrine growth factors, such as PDGF and TGF-beta.

Cyclooxygenase-1 and -2 expression in rheumatoid synovial tissues. Effects of interleukin-1 beta, phorbol ester, and corticosteroids.

High levels of immunoreactive cyclooxygenase (Cox; prostaglandin H synthase) are present in synovia from patients with rheumatoid arthritis (RA). We now show that the recently identified inducible isoform of Cox, Cox-2, is expressed in synovia from patients with RA. To further explore modulation of the Cox isoforms in RA synovial tissues, we examined the expression and modulation of Cox-1 and -2 in rheumatoid synovial explant cultures and cultured rheumatoid synovial fibroblast-like cells (synoviocytes). Immunoprecipitation of in vitro labeled proteins and Western blot analysis demonstrated the presence of both Cox-1 and -2 under basal conditions in freshly explanted rheumatoid synovial tissues. De novo synthesis of Cox-2 polypeptide was enhanced by IL-1 beta or PMA, and dramatically suppressed by dexamethasone (dex). Cox-1 expression, under the same conditions, showed only minor variation. Since mRNA for Cox-2 is highly unstable, we examined the regulation of Cox-2 transcripts in cultured rheumatoid synoviocytes. Under basal conditions both Cox-1 and -2 mRNAs were present at low levels, but Cox-2 mRNA was markedly increased by treatment with IL-1 beta or PMA. dex markedly suppressed the induction of Cox-2 mRNA. In sharp contrast, Cox-1 transcripts were not modulated by IL-1 beta or dex. These data suggest that modulation of Cox-2 expression by IL-1 beta and corticosteroids may be an important component of the inflammatory process in synovial tissues from patients with RA.

Inferior petrosal sinus sampling in healthy subjects reveals a unilateral corticotropin-releasing hormone-induced arginine vasopressin release associated with ipsilateral adrenocorticotropin secretion.

Arginine vasopressin (AVP) acts synergistically with corticotropin-releasing hormone (CRH) to stimulate ACTH release from the anterior pituitary. In a previous study of bilateral simultaneous inferior petrosal sinus (IPS) sampling in healthy human subjects, we observed lateralized ACTH secretion, suggesting lateralized secretion of an ACTH-regulating hypothalamic factor. To investigate this possibility, we measured ACTH, CRH, AVP, and oxytocin (OT) levels in the IPS and the peripheral circulation in nine normal volunteers, before and after 1 microgram/kg i.v. bolus ovine CRH (oCRH). At baseline, ACTH, AVP, and OT exhibited a significant (P < 0.05) two to threefold intersinus gradient (ISG), indicating the existence of a dominant petrosal sinus. Endogenous CRH was undetectable in all samples. Despite similar exogenous oCRH levels in both petrosal sinuses, oCRH caused a significant increase (P < 0.001) in the ACTH ISG (15.8 +/- 5.6, mean +/- SEM), suggesting increased responsiveness of one dominant side of the anterior pituitary. This was associated with an ipsilateral CRH-induced AVP release and a significant increase (P < 0.01) in the AVP ISG (8.6 +/- 2.3), suggesting lateralized AVP secretion by the hypothalamus. Furthermore, the increased AVP ISG after oCRH correlated strongly with the ACTH ISG (r = 0.92, P < 0.01). oCRH administration did not affect OT. These findings suggest that there is a dominant petrosal sinus in healthy volunteers that appears to reflect a dominant side of the adenohypophysis, characterized by increased functional activity and/or responsiveness of the pituitary corticotrophs. This may reflect lateralized hypothalamic and/or suprahypothalamic function resulting in CRH-responsive lateralized secretion of AVP from parvocellular and/or magnocellular axons in the median eminence and the posterior pituitary. Although the functional and teleologic significance of these findings remains to be investigated, our data suggest a novel mechanism for CRH-mediated ACTH release, namely CRH-induced release of AVP which then enhances CRH action on the corticotrophs. Furthermore, our data represent the first direct evidence for the concept of brain lateralization with respect to neuroendocrine secretion.

Coexpression of phosphotyrosine-containing proteins, platelet-derived growth factor-B, and fibroblast growth factor-1 in situ in synovial tissues of patients with rheumatoid arthritis and Lewis rats with adjuvant or streptococcal cell wall arthritis.

Fibroblast growth factor (FGF)-1 and PDGF-B-like factors have been implicated in the pathobiology of RA and animal models of this disease. Since the receptors for FGF-1 and PDGF are tyrosine kinases, we examined the expression of tyrosine phosphorylated proteins (phosphotyrosine, P-Tyr) in synovial tissues from patients with RA and osteoarthritis (OA), and rats with streptococcal cell wall (SCW) and adjuvant arthritis (AA). Synovia from patients with RA and LEW/N rats with SCW and AA arthritis, in contrast to controls, stained intensely with anti-P-Tyr antibody. The staining colocalized with PDGF-B and FGF-1 staining. Comparative immunoblot analysis showed markedly enhanced expression of a 45-kD P-Tyr protein in the inflamed synovia. Treatment with physiological concentrations of dexamethasone suppressed both arthritis and P-Tyr expression in AA. P-Tyr was only transiently expressed in athymic nude Lewis rats and was not detected in relatively arthritis-resistant F344/N rats. These data suggest that (a) FGF-1 and PDGF-B-like factors are upregulated and may induce tyrosine phosphorylation of proteins in vivo in inflammatory joint diseases, (b) persistent high level P-Tyr expression is T lymphocyte dependent, correlates with disease severity, and is strain dependent in rats, (c) corticosteroids, in physiological concentrations, downregulate P-Tyr expression in these lesions.

L-tryptophan implicated in human eosinophilia-myalgia syndrome causes fasciitis and perimyositis in the Lewis rat.

Tryptophan-associated eosinophilia-myalgia syndrome (L-TRP-EMS) is a newly described syndrome which occurred in epidemic fashion in the United States in the summer and fall of 1989. Epidemiologic data has linked the syndrome to intake of L-tryptophan (L-TRP) from one specific manufacturer, but the precise etiologic compound(s) must be established by replication of the syndrome in an appropriate animal model. In this study, implicated L-TRP, United States Pharmacopeia (USP) grade L-TRP, or vehicle was administered by gavage in a blinded fashion for 38 d to female Lewis rats at doses comparable with those ingested by patients who developed the eosinophilia-myalgia syndrome. Animals receiving implicated L-TRP, but not those receiving USP grade L-TRP or vehicle, developed histologic signs consistent with fasciitis and perimyositis, specific pathologic features of human L-TRP-EMS. Peripheral blood eosinophilia was not observed. Hypothalamic corticotropin releasing hormone mRNA levels were lower and plasma corticosterone levels tended to be lower in the animals that received implicated L-TRP. Plasma L-kynurenine was higher in both L-TRP-treated groups compared to the vehicle-treated animals. The female Lewis rat is known to be susceptible to a wide variety of inflammatory diseases. Identification of specific inflammatory changes in this rat following exposure to implicated L-TRP indicates that this animal model will be important in subsequent investigations into the etiology, pathogenesis, and treatment of human L-TRP-EMS.

Mapping autoimmunity genes.

Rat and mouse models for the major human autoimmune/inflammatory diseases are under intense genetic scrutiny. Genome-wide linkage studies reveal that each model is regulated by multiple genetic loci. Many of these loci colocalize to homologous genomic regions associated with several different autoimmune diseases of mice, rats and humans. Candidate genes are being identified. Polymorphic alleles associated with these chromosomal segments may represent predisposing genetic elements common to a number of human diseases with very different clinical presentations.

Expression of cyclooxygenase-1 and -2 in human colorectal cancer.

Several studies indicate that nonsteroidal anti-inflammatory drugs including indomethacin, aspirin, sulindac, and piroxicam reduce the risk of colon cancer. Furthermore, nonsteroidal anti-inflammatory drugs that inhibit the cyclooxygenase (COX) enzyme were shown to inhibit the development of colon cancer in animal models of carcinogenesis. Non-steroidal anti-inflammatory drugs inhibit the enzymatic activity of both the constitutive (COX-1) and inducible (COX-2) isoforms of COX enzyme. We have investigated the expression of COX-1 and COX-2 polypeptides in human colon cancer tissues using immunohistochemistry. Enhanced COX-2 expression was observed in colon cancer tissues from 15 subjects with clinically diagnosed colorectal cancer. Marked COX-2 expression was observed in cancer cells, inflammatory cells, vascular endothelium, and fibroblasts of the lesional tissues compared with the nonlesional and normal colon tissues. The extent and intensity of the immunoreactive COX-2 in cancer cells was much greater than that of the other cell types. In contrast, the expression of COX-1 polypeptide was weak in both normal and cancerous specimens. These data suggest that the enhanced expression of the COX-2 gene in colon cancer tissues may contribute to the enhanced synthesis of prostaglandin E2 by the colon cancer tissues. Enhanced expression of COX-2 may play a role in the pathogenesis of colon cancer. Furthermore, selective inhibition of COX-2 may prove to be more efficacious in the retardation of colon cancer development.