Cartilage Wear Particles Induce an Inflammatory Response Similar to Cytokines in Human Fibroblast-Like Synoviocytes

The synovium plays a key role in the development of osteoarthritis, as evidenced by pathological changes to the tissue observed in both early and late stages of the disease. One such change is the attachment of cartilage wear particles to the synovial intima. While this phenomenon has been well observed clinically, little is known of the biological effects that such particles have on resident cells in the synovium. The present work investigates the hypothesis that cartilage wear particles elicit a pro-inflammatory response in diseased and healthy human fibroblast-like synoviocytes, like that induced by key cytokines in osteoarthritis. Fibroblast-like synoviocytes from 15 osteoarthritic human donors and a subset of three non-osteoarthritic donors were exposed to cartilage wear particles, interleukin-1α or tumor necrosis factor-α for 6 days and analyzed for proliferation, matrix production, and release of pro-inflammatory mediators and degradative enzymes. Wear particles significantly increased proliferation and release of nitric oxide, interleukin-6 and -8, and matrix metalloproteinase-9, -10, and -13 in osteoarthritic synoviocytes, mirroring the effects of both cytokines, with similar trends in non-osteoarthritic cells. These results suggest that cartilage wear particles are a relevant physical factor in the osteoarthritic environment, perpetuating the pro-inflammatory and pro-degradative cascade by modulating synoviocyte behavior at early and late stages of the disease. Future work points to therapeutic strategies for slowing disease progression that target cell-particle interactions. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1979-1987, 2019.

A Functional Tissue-Engineered Synovium Model to Study Osteoarthritis Progression and Treatment

IMPACT STATEMENT

The synovium envelops the diarthrodial joint and plays a key regulatory role in defining the composition of the synovial fluid through filtration and biosynthesis of critical boundary lubricants. Synovium changes often precede cartilage damage in osteoarthritis. We describe a novel in vitro tissue engineered model, validated against native synovium explants, to investigate the structure-function of synovium through quantitative solute transport measures. Synovium was evaluated in the presence of a proinflammatory cytokine, interleukin-1, or the clinically relevant corticosteroid, dexamethasone. We anticipate that a better understanding of synovium transport would support efforts to develop more effective strategies aimed at restoring joint health.

Toward understanding the role of cartilage particulates in synovial inflammation

OBJECTIVE

Arthroscopy with lavage and synovectomy can remove tissue debris from the joint space and the synovial lining to provide pain relief to patients with osteoarthritis (OA). Here, we developed an in vitro model to study the interaction of cartilage wear particles with fibroblast-like synoviocytes (FLS) to better understand the interplay of cartilage particulates with cytokines on cells of the synovium.

METHOD

In this study sub-10 μm cartilage particles or 1 μm latex particles were co-cultured with FLS ±10 ng/mL interleukin-1α (IL-1α) or tumor necrosis factor-α (TNF-α). Samples were analyzed for DNA, glycosaminoglycan (GAG), and collagen, and media samples were analyzed for media GAG, nitric oxide (NO) and prostaglandin-E2 (PGE2). The nature of the physical interaction between the particles and FLS was determined by microscopy.

RESULTS

Both latex and cartilage particles could be phagocytosed by FLS. Cartilage particles were internalized and attached to the surface of both dense monolayers and individual cells. Co-culture of FLS with cartilage particulates resulted in a significant increase in cell sheet DNA and collagen content as well as NO and PGE2 synthesis compared to control and latex treated groups.

CONCLUSION

The proliferative response of FLS to cartilage wear particles resulted in an overall increase in extracellular matrix (ECM) content, analogous to the thickening of the synovial lining observed in OA patients. Understanding how cartilage particles interface with the synovium may provide insight into how this interaction contributes to OA progression and may guide the role of lavage and synovectomy for degenerative disease.

Fibroblast-like synoviocyte mechanosensitivity to fluid shear is modulated by interleukin-1α

Fibroblast-like synoviocytes (FLS) reside in the synovial membrane of diarthrodial joints and are exposed to a dynamic fluid environment that presents both physical and chemical stimuli. The ability of FLS to sense and respond to these stimuli plays a key role in their normal function, and is implicated in the alterations to function that occur in osteoarthritis (OA). The present work characterizes the response of FLS to fluid flow-induced shear stress via real-time calcium imaging, and tests the hypothesis that this response is modulated by interleukin-1α (IL-1α), a cytokine elevated in OA. FLS demonstrated a robust calcium signaling response to fluid shear that was dose dependent upon stress level and required both external and internal calcium sources. Preconditioning with 10ng/mL IL-1α for 24h heightened this shear stress response by significantly increasing the percent of responding cells and peak magnitude, while significantly decreasing the time for a peak to occur. Intercellular communication via gap junctions was found to account for a portion of the FLS population response in normal conditions, and was significantly increased by IL-1α preconditioning. IL-1α was also found to significantly increase average length and incidence of the primary cilium, an organelle commonly implicated in shear mechanosensing. These findings suggest that the elevated levels of IL-1α found in the OA environment heighten FLS sensitivity to fluid shear by altering both intercellular communication and individual cell sensitivity, which could affect downstream functions and contribute to progression of the disease state.

Transient expression of the diseased phenotype of osteoarthritic chondrocytes in engineered cartilage

Due to the degradation of osteoarthritic (OA) cartilage in post-traumatic OA (PTOA), these tissues are challenging to study and manipulate in vitro. In this study, chondrocytes isolated from either PTOA (meniscal-release (MR) model) or normal (contralateral limb) cartilage of canine knee joints were used to form micropellets to assess the maintenance of the OA chondrocyte phenotype in vitro. Media samples from the micropellet cultures were used to measure matrix metalloproteinase (MMP), chemokine, and cytokine concentrations. Significant differences in matrix synthesis were observed as a function of disease with OA chondrocytes generally synthesizing more extracellular matrix with increasing time in culture. No donor dependent differences were detected. Luminex multiplex analysis of pellet culture media showed disease and time-dependent differences in interleukin (IL)-8, keratinocyte chemoattractant (KC)-like protein, MMP-1, MMP-2, and MMP-3, which are differentially expressed in OA. This memory of their diseased phenotype persists for the first 2 weeks of culture. These results demonstrate the potential to use chondrocytes from an animal model of OA to study phenotype alterations during the progression and treatment of OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:829-836, 2017.

The lymphocyte in immunology: from James B. Murphy to James L. Gowans

Between 1912 and 1921, James Murphy established conclusively the role of the lymphocyte in tissue and tumor graft rejection and in protection against infection. Contemporary mainstream immunology paid little attention to these findings, until the lymphocyte was "rediscovered" with the advent of modern cellular immunology after the mid-1950s.

The most elegant immunological experiment of the XIX century

When we remember that immunology was barely a decade old and knowledge of circulating antibodies only two years old when Ehrlich performed the experiments described, we can appreciate the inventiveness of his experimental designs. With little wasted effort he planned simple and rapid experiments to answer crucial questions about the mechanism of passive transfer of antibody from mother to fetus to suckling young. Most remarkable and difficult were the foster mother experiments, as anyone who has tried these with mice will attest. But they were judged to be critical and thus were pursued with ultimate success. These experiments would not be improved upon for 60 years, when the identification of immunoglobulin classes made differential transplacental and transglandular passage of immunoglobulins an object of interest. To conceive of studying the kinetics of the immune response by measuring changes in antibody concentration in the milk of lactating animals was yet another demonstration of the fertile imagination that had contributed so much to histology and hematology, and would soon contribute equally to experimental oncology and to scientific pharmacology.

There is only one immune system! The view from immunopathology

The generators of B and T cell diversity produce specificities for both autochthonous and exogenous paratopes. A wide variety of positive and negative, central and peripheral mechanisms has evolved to regulate the immune response. All potential immunogens are recognized by the system using the same set of 'rules', without discrimination between 'self' and 'nonself' or between the 'toxic' and the 'benign'. In every response, whether positive or negative, the factors mobilized and the balance between protection and damage depend upon the quality, quantity, location, and timing of immunogen presentation, as well as upon properties of the host.

The Hsp organizer protein hop enhances the rate of but is not essential for glucocorticoid receptor folding by the multiprotein Hsp90-based chaperone system

A system consisting of five purified proteins: Hsp90, Hsp70, Hop, Hsp40, and p23, acts as a machinery for assembly of glucocorticoid receptor (GR).Hsp90 heterocomplexes. Hop binds independently to Hsp90 and to Hsp70 to form a Hsp90.Hop.Hsp70.Hsp40 complex that is sufficient to convert the GR to its steroid binding form, and this four-protein complex will form stable GR.Hsp90 heterocomplexes if p23 is added to the system (Dittmar, K. D., Banach, M., Galigniana, M. D., and Pratt, W. B. (1998) J. Biol. Chem. 273, 7358-7366). Hop has been considered essential for the formation of receptor.Hsp90 heterocomplexes and GR folding. Here we use Hsp90 and Hsp70 purified free of all traces of Hop and Hsp40 to show that Hop is not required for GR.Hsp90 heterocomplex assembly and activation of steroid binding activity. Rather, Hop enhances the rate of the process. We also show that Hsp40 is not essential for GR folding by the five-protein system but enhances a process that occurs less effectively when it is not present. By carrying out assembly in the presence of radiolabeled steroid to bind to the GR as soon as it is converted to the steroid binding state, we show that the folding change is brought about by only two essential components, Hsp90 and Hsp70, and that Hop, Hsp40, and p23 act as nonessential co-chaperones.

Pasteur, Pastorians, and the dawn of immunology: the importance of specificity

Throughout his career, the problems that attracted Louis Pasteur almost invariably involved considerations of specificity of structure and/or of action. Thus, his work on asymmetric crystals showed that chemical form not only specifies crystalline structure, but affects the affinity of ferments as well. In his studies of diseases of silkworms, of beer, and of wine, he could unerringly distinguish with the microscope the specific agents of disease. From this emerged his concept of the specificity of species and against the nonspecificity of spontaneous generation, whence the germ theory of disease. It was in the new field of immunology, however, where the manifestations of an exquisite specificity were most clearly seen. Here, Pasteur's vaccines worked because he chose the specific pathogen in order to induce a specific immunity, and he succeeded each time. But the two most prominent Pastorian successors in immunology, Elie Metchnikoff and Jules Bordet, were not equally successful. Although each contributed significantly to the birth of immunology, each advanced a theory that neglected the principle of specificity and paid a price in consequence. Metchnikoff's phagocytic theory of immunity could not survive the demonstrable specificity of humoral antibodies, while Bordet's physical adsorptive concept of the antibody-cell interaction quickly fell to Paul Ehrlich's demonstration of the stereochemical determination of immunological specificity.

Different regions of the immunophilin FKBP52 determine its association with the glucocorticoid receptor, hsp90, and cytoplasmic dynein

FKBP52 is a high molecular mass immunophilin possessing peptidylprolyl isomerase (PPIase) activity that is inhibited by the immunosuppressant drug FK506. FKBP52 is a component of steroid receptor.hsp90 heterocomplexes, and it binds to hsp90 via a region containing three tetratricopeptide repeats (TPRs). Here we demonstrate by cross-linking of the purified proteins that there is one binding site for FKBP52/dimer of hsp90. This accounts for the common heterotetrameric structure of native receptor heterocomplexes being 1 molecule of receptor, 2 molecules of hsp90, and 1 molecule of a TPR domain protein. Immunoadsorption of FKBP52 from reticulocyte lysate also yields co-immunoadsorption of cytoplasmic dynein, and we show that co-immunoadsorption of dynein is competed by a fragment of FKBP52 containing its PPIase domain, but not by a TPR domain fragment that blocks FKBP52 binding to hsp90. Using purified proteins, we also show that FKBP52 binds directly to the hsp90-free glucocorticoid receptor. Because neither the PPIase fragment nor the TPR fragment affects the binding of FKBP52 to the glucocorticoid receptor under conditions in which they block FKBP52 binding to dynein or hsp90, respectively, different regions of FKBP52 must determine its association with these three proteins.

The seven amino acids (547-553) of rat glucocorticoid receptor required for steroid and hsp90 binding contain a functionally independent LXXLL motif that is critical for steroid binding

Hsp90 association with glucocorticoid receptors (GRs) is required for steroid binding. We recently reported that seven amino acids (547-553) overlapping the amino-terminal end of the rat GR ligand-binding domain are necessary for hsp90 binding, and consequently steroid binding. The role of a LXXLL motif at the COOH terminus of this sequence has now been analyzed by determining the properties of Leu to Ser mutations in full-length GR and glutathione S-transferase chimeras. Surprisingly, these mutations decreased steroid binding capacity without altering receptor levels, steroid binding affinity, or hsp90 binding. Single mutations in the context of the full-length receptor did not affect the transcriptional activity but the double mutant (L550S/L553S) was virtually inactive. This biological inactivity was found to be due to an increased rate of steroid dissociation from the activated mutant complex. These results, coupled with those from trypsin digestion studies, suggest a model in which the GR ligand-binding domain is viewed as having a "hinged pocket," with the hinge being in the region of the trypsin digestion site at Arg(651). The pocket would normally be kept shut via the intramolecular interactions of the LXXLL motif at amino acids 550-554 acting as a hydrophobic clasp.

A model for the cytoplasmic trafficking of signalling proteins involving the hsp90-binding immunophilins and p50cdc37

A number of transcription factors and protein kinases involved in signal transduction exist in heterocomplexes with the ubiquitous and essential protein chaperone hsp90. These signalling protein x hsp90 heterocomplexes are assembled by a multiprotein chaperone system comprising hsp90, hsp70, Hop, hsp40, and p23. In the case of transcription factors, the heterocomplexes with hsp90 also contain a high molecular weight immunophilin with tetratricopeptide repeat (TPR) motifs, such as FKBP52 or CyP-40. In the case of the protein kinases, the heterocomplexes contain p50cdc37. The immunophilins bind to a single TPR acceptor site on hsp90, and p50cdc37 binds to an adjacent site so that binding is exclusive for p50cdc37 or an immunophilin. Direct interaction of immunophilins with the transcription factors or p50cdc37 with the protein kinases leads to selection of different heterocomplexes after their assembly by a common mechanism. Studies with the glucocorticoid receptor, for which translocation from the cytoplasm to the nucleus is under hormonal control, suggest that dynamic assembly of the heterocomplexes is required for rapid movement of the receptor through the cytoplasm along cytoskeletal tracts. As for the similar short-range trafficking of vesicles along microtubules, there must be a mechanism for linking the signalling protein solutes to the molecular motors involved in movement. We present here a model in which the immunophilins and p50cdc37 target, respectively, the retrograde or anterograde direction of signalling protein movement by functioning as connectors that link the signalling proteins to the movement machinery.

Glucocorticoids stimulate the accumulation of lipids in the rat corpus luteum

We investigated the physiological basis for the trophic effect of glucocorticoids in rat corpora lutea in the absence of pituitary gonadotropins. Immature (Day 29) Sprague-Dawley rats were given eCG and hCG to induce the development of corpora lutea and were hypophysectomized on Day 32. Beginning on Day 40, rats received twice-daily s.c. injections of either dexamethasone (dex; 200 microg/rat/day) or vehicle (controls) and then were killed on Day 44. Plasma 20alpha-dihydroprogesterone, a major steroid produced by the corpora lutea, was higher (p </= 0.01) in dex-treated than in control rats (44.5 +/- 2.3 vs. 23.0 +/- 5.6 ng/ml). Dexamethasone treatment increased lipid droplets and lipid in the corpora lutea as revealed by electron microscopy and oil red O staining. Cholesterol esters were higher in corpora lutea of dex-treated rats compared to controls (14.8 +/- 1.1 vs. 2.2 +/- 0.5 microg/mg corpora lutea wet tissue, respectively; p </= 0.05). Another group of hypophysectomized rats was treated with either a high or a lower dosage of corticosterone, both of which caused an elevation to > 2-fold of plasma 20alpha-dihydroprogesterone concentration compared to controls. Glucocorticoid receptor protein (about 92 kDa) was detected in both luteal and nonluteal ovarian tissues in this animal model. These effects of glucocorticoids and the presence of the glucocorticoid receptor raise the possibility of a physiological role for glucocorticoids in the rat corpus luteum.

Paul Ehrlich's passion: the origins of his receptor immunology

In 1897, Paul Ehrlich published a selection theory of antibody formation that anticipated the theories of Jerne and Burnet by some 60 years. Ehrlich introduced into immunology the concept of the interaction of physiologically active substances with specific receptors, an idea that still dominates modern immunological thought. In this paper, we point out how Ehrlich's concept matured over 20 years, while it governed his studies in histological staining, in cell physiology, in hematology, and finally in his major contributions in experimental immunology.

Neuronal nitric-oxide synthase is regulated by the Hsp90-based chaperone system in vivo

It is established that the multiprotein heat shock protein 90 (hsp90)-based chaperone system acts on the ligand binding domain of the glucocorticoid receptor (GR) to form a GR.hsp90 heterocomplex and to convert the receptor ligand binding domain to the steroid-binding state. Treatment of cells with the hsp90 inhibitor geldanamycin inactivates steroid binding activity and increases the rate of GR turnover. We show here that a portion of neuronal nitric-oxide synthase (nNOS) exists as a molybdate-stabilized nNOS. hsp90 heterocomplex in the cytosolic fraction of human embryonic kidney 293 cells stably transfected with rat nNOS. Treatment of human embryonic kidney 293 cells with geldanamycin both decreases nNOS catalytic activity and increases the rate of nNOS turnover. Similarly, geldanamycin treatment of nNOS-expressing Sf9 cells partially inhibits nNOS activation by exogenous heme. Like the GR, purified heme-free apo-nNOS is activated by the DE52-retained fraction of rabbit reticulocyte lysate, which also assembles nNOS. hsp90 heterocomplexes. However, in contrast to the GR, heterocomplex assembly with hsp90 is not required for increased heme binding and nNOS activation in this cell-free system. We propose that, in vivo, where access by free heme is limited, the complete hsp90-based chaperone machinery is required for sustained opening of the heme binding cleft and nNOS activation, but in the heme-containing cell-free nNOS-activating system transient opening of the heme binding cleft without hsp90 is sufficient to facilitate heme binding.

High-molecular-weight FK506-binding proteins are components of heat-shock protein 90 heterocomplexes in wheat germ lysate

In animal cell lysates the multiprotein heat-shock protein 90 (hsp90)-based chaperone complexes consist of hsp70, hsp40, and p60. These complexes act to convert steroid hormone receptors to their steroid-binding state by assembling them into heterocomplexes with hsp90, p23, and one of several immunophilins. Wheat germ lysate also contains a hsp90-based chaperone system that can assemble the glucocorticoid receptor into a functional heterocomplex with hsp90. However, only two components of the heterocomplex-assembly system, hsp90 and hsp70, have thus far been identified. Recently, purified mammalian p23 preadsorbed with JJ3 antibody-protein A-Sepharose pellets was used to isolate a mammalian p23-wheat hsp90 heterocomplex from wheat germ lysate (J.K. Owens-Grillo, L.F. Stancato, K. Hoffmann, W.B. Pratt, and P. Krishna [1996] Biochemistry 35: 15249-15255). This heterocomplex was found to contain an immunophilin(s) of the FK506-binding class, as judged by binding of the radiolabeled immunosuppressant drug [3H]FK506 to the immune pellets in a specific manner. In the present study we identified the immunophilin components of this heterocomplex as FKBP73 and FKBP77, the two recently described high-molecular-weight FKBPs of wheat. In addition, we present evidence that the two FKBPs bind hsp90 via tetratricopeptide repeat domains. Our results demonstrate that binding of immunophilins to hsp90 via tetratricopeptide repeat domains is a conserved protein interaction in plants. Conservation of this protein-to-protein interaction in both plant and animal cells suggests that it is important for the biological action of the high-molecular-weight immunophilins.

Acute postictal cerebral imaging

BACKGROUND AND PURPOSE

Imaging of postictal patients is performed to investigate causes of seizure, such as space-occupying lesions or other "structural" processes; however, abnormalities may be found that reflect physiological or pathologic alterations due to seizure activity. The purpose of this study was to determine the brain imaging findings in patients in the immediate postictal period who presented with altered mental status or weakness.

METHODS

Ten patients who were examined for postictal neurologic derangement were studied (nine by CT and one by MR imaging) within 12 hours of ictus. Four of the CT studies and the one MR study included administration of contrast material. Follow-up examinations were performed 1 day to 11 months later. These studies were reviewed retrospectively.

RESULTS

CT findings included focal gyral swelling (10/10), effacement of adjacent cortical sulci (2/10), decreased gyral attenuation by CT (8/9), and mild to moderate gyral enhancement after injection of contrast material (5/5). MR imaging findings included gyral swelling, increased signal intensity on T2-weighted images, and enhancement after injection of contrast agent. The abnormalities were located in the frontal lobes (9/10, with bilateral involvement in 6/10), the parietal lobes (4/10), the temporal lobes (2/10), and the occipital lobe (1/10). Follow-up studies revealed complete or subtotal reversal of these abnormalities.

CONCLUSION

Although there are numerous causes of gyral swelling and enhancement, such as infarction and neoplasm, if these conditions are reversible and correspond to clinical findings, then the differential diagnosis is narrowed to postictal change, reversible ischemia, complicated migraine, or resolved inflammation/infection.

p50(cdc37) binds directly to the catalytic domain of Raf as well as to a site on hsp90 that is topologically adjacent to the tetratricopeptide repeat binding site

Several protein kinases (e.g. pp60(src), v-Raf) exist in heterocomplexes with hsp90 and a 50-kDa protein that is the mammalian homolog of the yeast cell cycle control protein Cdc37. In contrast, unliganded steroid receptors exist in heterocomplexes with hsp90 and a tetratricopeptide repeat (TPR) domain protein, such as an immunophilin. Although p50(cdc37) and TPR domain proteins bind directly to hsp90, p50(cdc37) is not present in native steroid receptor.hsp90 heterocomplexes. To obtain some insight as to how v-Raf selects predominantly hsp90.p50(cdc37) heterocomplexes, rather than hsp90.TPR protein heterocomplexes, we have examined the binding of p50(cdc37) to hsp90 and to Raf. We show that p50(cdc37) exists in separate hsp90 heterocomplexes from the TPR domain proteins and that intact TPR proteins compete for p50(cdc37) binding to hsp90 but a protein fragment containing a TPR domain does not. This suggests that the binding site for p50(cdc37) lies topologically adjacent to the TPR acceptor site on the surface of hsp90. Also, we show that p50(cdc37) binds directly to v-Raf, with the catalytic domain of Raf being sufficient. We propose that the combination of exclusive binding of p50(cdc37) versus a TPR domain protein to hsp90 plus direct binding of p50(cdc37) to Raf allows the protein kinase to select for the dominant hsp90.p50(cdc37) composition that is observed with a variety of protein kinase heterocomplexes immunoadsorbed from cytosols.

Changing trends in the etiologic diagnosis of uveitis

Just as different fads that seize the imagination of the general public are often carried to excess, so diagnostic or therapeutic fads may take over in the practice of medicine. Analysis of 33 surveys of the causes of uveitis reported by ophthalmologists over the course of 120 years shows how some diagnoses such as syphilis and tuberculosis fell from favor because tests ruled out these diseases, whereas others such as toxoplasmosis became popular because of the finding of the organism in a few cases by a famous ophthalmic pathologist. Yet others (pars planitis, sarcoidosis) were not even causes of disease, but rather merely descriptive, or the ocular component of a systemic disease whose etiology and pathogenesis remain unknown. We will examine the waxing and waning of these diagnostic categories and the impressive confidence of some clinicians in their own diagnostic acumen as they made diagnoses often unsupported by objective evidence.

On the mystique of the immunological self

Since the time of Paul Ehrlich 100 years ago, we have known that the immunological apparatus somehow inhibits most damaging autoimmune responses while permitting a response to exogenous immunogens. With the discovery of tolerance, the concept of immunological surveillance, and especially with the discovery of HLA restriction of T-cell recognition, the term "the immunological self" and the phrase "self-nonself discrimination" have gained wide currency. Immunology has been called "The Science of Self", and self-nonself discrimination has been assigned as the driving force for its complex evolution. The concept of self has thus been given such mystical trappings since the time of Macfarlane Burnet that recent workers have felt free to pronounce it the central paradigm of modern immunology, and to claim to overthrow it! In this article, we challenge some of the more egregious claims about the immunological self by recalling important historical findings, by reviewing the mechanisms of Darwinian evolution, and by remembering that the general pathology of immunogenic inflammation shows that the immune response cannot discriminate between the benign and the noxious.

Protein phosphatase 5 is a major component of glucocorticoid receptor.hsp90 complexes with properties of an FK506-binding immunophilin

Steroid receptors are recovered from hormone-free cells in multiprotein complexes containing hsp90, p23, an immunophilin, and often some hsp70. The immunophilin, which can be of the FK506- or cyclosporin A-binding class, binds to hsp90 via its tetratricopeptide repeat (TPR) domain, and different receptor heterocomplexes exist depending upon which immunophilin occupies the TPR-binding region of hsp90. We have recently reported that a protein serine/threonine phosphatase that is designated PP5 and contains four TPRs binds to hsp90 and is co-purified with the glucocorticoid receptor (GR) (Chen, M.-S., Silverstein, A. M., Pratt, W. B., and Chinkers, M. (1996) J. Biol. Chem. 271, 32315-32320). In this work, we show that PP5 is recovered with both GR that is nuclear and GR that is cytoplasmic in hormone-free cells. Approximately one-half of the GR.hsp90 heterocomplexes in L cell cytosol contains an immunophilin with high affinity FK506 binding activity, such as FKBP51 or FKBP52, and approximately 35% contains PP5. Only a small (but undetermined) fraction of the native GR.hsp90 heterocomplexes contain the cyclosporin A-binding immunophilin CyP-40. PP5, FKBP52, and CyP-40 exist in separate heterocomplexes with hsp90, and competition binding experiments with the PP5 TPR domain suggest that the three proteins occupy a common binding site on hsp90. A 55-residue connecting region between the N-terminal TPR domain of human PP5 and its C-terminal phosphatase domain has 50% amino acid homology and 22% identity with the central portion of the peptidylprolyl isomerase domain of human FKBP52. Of the 9 residues in this portion of FKBP52 involved in high affinity interactions with FK506, 3 residues are retained and 4 have homologous substitutions in PP5. Although immunoadsorbed PP5 did not bind [3H]FK506, we found that both rabbit PP5 in reticulocyte lysate and purified rat PP5 were specifically retained by an FK506 affinity matrix. Thus, we propose that PP5 possesses properties of an immunophilin with low affinity FK506 binding activity and that it determines a major portion of the native GR heterocomplexes in L cell cytosol.

Geldanamycin, a heat shock protein 90-binding benzoquinone ansamycin, inhibits steroid-dependent translocation of the glucocorticoid receptor from the cytoplasm to the nucleus

When they are translated, steroid receptors are assembled into a multiprotein complex containing hsp90, p23, an immunophilin, and often some hsp70. Some of the receptors, such as that for progesterone, have nuclear localization signals that are functional in the absence of hormone, and they move into the nucleus where they exist in the same multiprotein heterocomplex with hsp90. Other receptors, such as the glucocorticoid receptor, are localized predominantly in the cytoplasm in the absence of hormone and move into the nucleus in a hormone-dependent fashion. We have previously proposed that hsp90 and the immunophilin play a role in receptor trafficking [Pratt, W. B. (1993) J. Biol. Chem. 268, 21455-21458]. In this work, we show that treatment of L cells with geldanamycin, a benzoquinone ansamycin that binds to hsp90 and disrupts its function, impedes dexamethasone-dependent trafficking of the glucocorticoid receptor from the cytoplasm to the nucleus. Because geldanamycin treatment of hormone-free cells causes a rapid loss of steroid binding activity, receptors were prebound with dexamethasone by incubating cells with hormone at 0 degrees C prior to shifting the temperature to 37 degrees C for 20 min to permit receptor transformation and translocation in the presence or absence of geldanamycin. Geldanamycin does not cause steroid to dissociate from prebound receptors, and it does not inhibit hormone-mediated receptor transformation assayed by conversion to the DNA-binding state. However, as reported previously for the progesterone receptor, geldanamycin blocks assembly of the glucocorticoid receptor-hsp90 heterocomplex at an intermediate state of assembly where the receptor is bound to hsp70 and p60, both of which are required components in the assembly mechanism. Our observations support the proposal that dynamic association of receptors with hsp90 is required for receptor translocation from the cytoplasm to the nucleus.

The hsp90-binding antibiotic geldanamycin decreases Raf levels and epidermal growth factor signaling without disrupting formation of signaling complexes or reducing the specific enzymatic activity of Raf kinase

We have expressed the mitogenic signaling proteins Src, Ras, Raf-1, Mek (MAP kinase kinase), and Erk (MAP kinase) in baculovirus-infected Sf9 insect cells in order to study a potential role for the chaperone hsp90 in formation of multiprotein complexes. One such complex obtained by immunoadsorption with anti-Ras antibody of cytosol prepared from cells simultaneously expressing Ras, Raf, Mek, and Erk contained Ras, Raf, and Erk. To detect directly the protein-protein interactions involved in forming multiprotein complexes, we combined cytosols from single infections in vitro in all possible combinations of protein pairs. We detected complexes between Ras.Raf, Ras.Src, Raf.Mek, and Raf.Src, but no complex containing Erk was obtained by mixing cytosols. Thus, cellular factors appear to be required for assembly of the Erk-containing multiprotein complex. One cellular factor thought to be involved in signaling protein complex formation is the chaperone hsp90, and we show that Src, Raf, and Mek are each complexed with insect hsp90. Treatment of Sf9 cells with geldanamycin, a benzoquinone ansamycin that binds to hsp90 and disrupts its function, did not decrease coadsorption of either Raf or Erk with Ras, although it did decrease the level of cytosolic Raf. To study geldanamycin action, we treated rat 3Y1 fibroblasts expressing v-Raf and showed that the antibiotic blocked assembly of Raf.hsp90 complexes at an intermediate stage of assembly where Raf is still bound to the p60 and hsp70 components of the assembly mechanism. As in Sf9 cells, Raf levels decline with geldanamycin treatment of 3Y1 cells. To determine if geldanamycin affects mitogenic response, we treated HeLa cells with epidermal growth factor (EGF) and showed that geldanamycin treatment decreased EGF signaling and decreased the level of Raf protein without affecting the EGF-mediated increase in Raf kinase activity. We conclude that hsp90 is not required for forming complexes between the mitogenic signaling proteins or for Raf kinase activity and that EGF signaling is decreased indirectly by geldanamycin because the antibiotic increases degradation of Raf and perhaps other components of the signaling pathway.

The tetratricopeptide repeat domain of protein phosphatase 5 mediates binding to glucocorticoid receptor heterocomplexes and acts as a dominant negative mutant

We previously identified a protein-serine phosphatase designated PP5, based on the binding of its tetratricopeptide repeat (TPR) domain to the atrial natriuretic peptide receptor (Chinkers, M. (1994) Proc. Natl. Acad. Sci. U. S. A. 91, 11075-11079). We have now identified another protein complex to which PP5 is targeted through its TPR domain. A 90-kDa protein, identified as heat shock protein 90 (hsp90) by immunoblotting, specifically co-immunoprecipitated from COS-7 cell lysates with the FLAG-tagged TPR domain of PP5. hsp90 also co-immunoprecipitated with full-length FLAG-tagged PP5 overexpressed in COS-7 cells and with endogenous PP5 from untransfected COS-7 cells or rat brain. During gel filtration, PP5 and hsp90 comigrated in a high molecular weight complex. Since glucocorticoid receptors (GR) exist as large heterocomplexes containing hsp90 bound to TPR proteins, we hypothesized that PP5 might be associated with these complexes. Consistent with this hypothesis, PP5 specifically co-immunoprecipitated with GR from mouse L cell lysates. To test the functional importance of this TPR-mediated association in living cells, we used a dominant negative PP5 mutant consisting only of its TPR domain. The mutant inhibited GR-mediated transactivation by approximately 70% in transfected CV-1 cells. This is the first evidence that the TPR proteins in steroid receptor heterocomplexes may be required for signaling in vivo.

Paul Ehrlich: the founding of pediatric immunology

In 1892-93, Paul Ehrlich published a series of experiments on the passive transfer of maternal antibody to fetus and newborn that deserve to be better known. He pointed out the importance of mother's milk to neonatal well-being. He was the first to define the difference between active and passive immunity. He was the first to demonstrate immune elimination of antigen and to explain the significance of each phase of the kinetics of the anamnestic antibody response. We point out how elegant were these early experiments and how far in advance of their times.

Use of the thiol-specific derivatizing agent N-iodoacetyl-3-[125I]iodotyrosine to demonstrate conformational differences between the unbound and hsp90-bound glucocorticoid receptor hormone binding domain

The hormone binding domain (HBD) of the glucocorticoid receptor (GR) contains five cysteine residues, with three of them being spaced close to one another in the steroid binding pocket. The HBD also contains the contact region for the chaperone protein hsp90, which must be bound to the GR for it to have a steroid binding conformation. Binding of hsp90 to the receptor through its HBD inactivates the DNA binding domain (DBD). The DBD contains a number of cysteines essential to its DNA binding activity. Here, we assess the effects of hsp90 binding on the accessibility of cysteine residues in both the HBD and DBD to derivatization by a thiol-specific reagent. We report that N-iodoacetyltyrosine (IAT) inactivates steroid binding activity of the immunopurified, untransformed GR.hsp90 complex in a manner that is prevented by the sulfhydryl reagents cysteine and dithiothreitol but is not reversed by them. The 125I-labeled IAT derivative N-iodoacetyl-3-[125I]iodotyrosine ([125I]IAIT) covalently labels the immunopurified, hsp90-bound receptor in a thiol-specific manner. Dissociation of hsp90 leads to an approximately 2-fold increase in [125I]IAIT labeling of the full-length, 100-kDa GR. The increase in thiol labeling is related to the presence of hsp90 because it is blocked by molybdate, which prevents hsp90 dissociation. Cleavage of the [125I]IAIT-labeled receptor with trypsin yields a 15-kDa labeled fragment containing the DBD and a 30-kDa labeled fragment containing all of the cysteines in the HBD and the contact region for hsp90. Dissociation of hsp90 from the GR results in a 2.3-fold increase in [125I]IAIT labeling of the 15-kDa fragment and a 50% decrease in labeling of the 30-kDa fragment. These data are consistent with the proposal that dissociation of hsp90 from the GR produces a conformational change in the HBD such that some of the thiols that are exposed in the GR*hsp90 complex become buried and are no longer accessible to the [125I]IAIT probe. In contrast, binding of the GR to hsp90 restricts access of cysteines in the DBD to this small thiol-derivatizing agent, a restriction that is relieved as a result of unmasking or conformational change accompanying hsp90 dissociation.

MRI of lumbar intervertebral discs. Diurnal variations in signal intensities

STUDY DESIGN

Eight volunteers underwent magnetic resonance imaging scans of their lumbar spines to determine diurnal variations in the scan results.

OBJECTIVES

Magnetic resonance imaging of the lumbar spine typically is obtained under the assumption that results are not influenced by the time of day the scan is performed. To validate this assumption, asymptomatic volunteers had magnetic resonance images made of their lumbar spines, twice in one day.

SUMMARY OF BACKGROUND DATA

No reports in the literature have indicated visible diurnal variations in magnetic resonance imaging of the spine.

METHODS

Two magnetic resonance imaging scans were obtained of each volunteer's lumbar spine, the first 1 to 1.5 hours after waking and the second 8 to 10 hours later. The signal intensity was measured from each disc and mathematical standardization was performed against a saline phantom. Changes in disc height and bulge also were measured. Two blinded neuroradiologists reviewed each scan.

RESULTS

Thirty-nine lumbar discs were studied. No visible changes could be detected between scans by blinded observers. However, the calculated signal intensity change was an average loss of 13.5%. An increase in disc bulge was measured in 48.6% of the discs.

CONCLUSIONS

In this group of asymptomatic volunteers, the time of day that a magnetic resonance imaging scan was obtained did not influence the visual interpretation.

From the forehead of Zeus: the ontogeny of the immune response

Many of the most important developments that result in a fully functioning vertebrate immune system take place in the developing fetus. From a variety of gene segments there is assembled in B cells a congeries of antibody combining sites, one to a cell, which form the greater part of the large repertoire of immunological specificities that characterise the system. This capability is further expanded later by somatic mutations. Just as immunoglobulin isotypes are produced sequentially (IgM, IgD, IgG, IgE, IgA) as they are read along the chromosome, so does the fetus and neonate manifest immunological competence sequentially to different antigens by employing variable region germline genes as they appear along the chromosome. The generation of T cell receptor diversity is accomplished by a similar mechanism of gene segment translocations. Each stage in the lineage of T and B cells is associated with the appearance of unique combinations of surface molecular markers, which in T cells characterise also the specialised functions of different subsets. If the immune system does not spring forth quite fully formed from the evolved vertebrate genome, as Athena did from the forehead of Zeus, ontogenetic mechanisms have made it very nearly complete.

The structure and dynamics of immunology, 1951-1972: a prosopographical study of international meetings

Immunology underwent a major change in direction during the 1950s and 1960s, from immunochemistry to immunobiology. A quantitative analysis of the participants at a large number of immunological meetings held during this critical period reveals much about the inner dynamics of the discipline. This new approach enables us to define the scientific leadership of the discipline and of its emerging subdisciplines, the interests of "mainstream" immunology, and when fields such as transplantation and allergy begin to join the mainstream. It is also suggested that some of these meetings, in addition to reflecting changes within the field, may have contributed substantially to these changes. Further, many of these meetings served to promote the institutionalization of the discipline and of its subdisciplines.

Participation in scientific meetings: a new prosopographical approach to the disciplinary history of science--the case of immunology, 1951-72

To handle the enormous amount of sources in modern and contemporary science, the historian can use different quantitative methods, particularly varieties of citation analysis. So far, all these methods have been based on publication data. Taking as its point of departure the fact that meetings constitute a pervasive, yet neglected, aspect of science, this paper introduces analysis of participation in scientific meetings. The strength of this new prosopographical method is illustrated by an analysis of international immunological meetings in the period 1951-72. Frequency of participation in meetings seems to be correlated to professional standing in immunology. By means of cluster analysis of participation data, the subdisciplinary structure and dynamics of immunology can be reconstructed.

Endoscopic paranasal sinus surgery: radiographic evaluation of severe complications

PURPOSE

To report our experience with the radiographic evaluation of severe complications resulting from the functional endoscopic sinus surgery (FESS) procedure.

PATIENTS

Ten major complications were reviewed retrospectively.

FINDINGS

Ten major complications occurred. Eight of 10 had injury to the floor of the anterior cranial fossa, fovea ethmoidalis (roof of the ethmoid sinus), or roof of the sphenoid sinus. Six patients presented with meningitis or rhinorrhea, two presented with headache and massive pneumocephalus; one patient who presented with meningitis had a large nasal frontal encephalocele. Noncontrast brain CT that included the paranasal sinuses adequately evaluated the source of pneumocephalus. Thin-section coronal CT accurately predicted the site of leak in five patients. Both coronal sinus CT and MR imaging were useful to confirm the nasal encephalocele. Two of 10 had vascular injury secondary to FESS. One patient presented with subarachnoid hemorrhage seen on noncontrast CT and cerebral angiography demonstrated an aneurysm of the anterior cerebral artery. The second patient suffered severe intraoperative hemorrhage. Emergency angiography revealed a pseudoaneurysm of the cavernous carotid artery, and balloon occlusion of the artery was performed. No deaths occurred in this series.

CONCLUSION

Radiologists should be familiar with the rare, but potential complications of this commonly performed procedure in order to help direct the work-up in an efficacious manner.

The dynamics of conceptual change in twentieth century immunology

I have attempted here to define three distinct eras in the 110-year history of the discipline of immunology. The first, extending from 1880 to about the First World War, centered around the new bacteriology and infectious diseases, and had a distinctly medical orientation. Several of the components of the original research program in immunology failed to maintain their original momentum or to fulfill their initial high promise, and went into decline. These include the development of new vaccines, serotherapeutic approaches, the study of cellular immunity, and the study of diseases that might be mediated by cytotoxic antibodies. Two other subprograms followed a somewhat different course; the study of anaphylaxis and related diseases passed primarily into the hands of clinical allergists, while the development and adaptation of serodiagnostic techniques passed into the hands of the new discipline of serology, both fields out of the mainstream of post-World War I immunology. As interest in the components of the old program was falling away, there developed a new area of interest in immunology. Leadership in the field devolved upon a new group of individuals with a predominantly chemical orientation to the study of antigens and antibodies, who pursued a research program and developed a theoretical base that reflected this orientation well. It may be interesting to examine more closely the forces responsible for this shift in emphasis. When interest in the old areas waned, the medically oriented practitioners did not switch to more immunochemical lines, but went in other directions. Karl Landsteiner was the only prominent "old-timer" who contributed significantly to the newer immunology, and it was his work that set the tone and attracted the new generation of immunochemists who became the reigning Denkkollektiv. A science does not change its precepts and approaches spontaneously; it is moved to the new position by those who explore fertile new areas. This is not to say, however, that there was no longer interesting and important work to be done along the old lines--it was just that such work was no longer "fashionable", as the reception of the work of Dienes, of Rich, of Rivers, and of the early Medawar illustrates. Whereas the earlier immunological program had interacted extensively with many different fields of biology and medicine, the immunochemical era was characterized by a relative introversion, as compared with the broad influence exerted by the earlier immunological program (92). We can date this second era from about the First World War until the late 1950s and early 1960s.(ABSTRACT TRUNCATED AT 400 WORDS)

MR imaging of the brain in five members of a family with Pelizaeus-Merzbacher disease

MR imaging was performed in five members of a family afflicted with Pelizaeus-Merzbacher disease. The individuals imaged included a male proband, his mother, and three maternal uncles. Clinically affected members showed generalized white matter signal aberration consistent with dys- and demyelination, basal ganglia, and thalamic signal aberration suggestive of pathologic iron storage and diffuse brain atrophy. These findings are similar to those seen in other leukodystrophies. The proband's mother was normal by neurologic examination but showed a suspicious but not definitely abnormal similar pattern of basal ganglionic and white matter signal aberration. In our limited patient sample, MR appears to be able to: (1) demonstrate a pattern of imaging abnormalities characteristic of Pelizaeus-Merzbacher disease (we do not know if this pattern is specific); (2) potentially detect the obligate carrier state; and (3) detect the facultative carrier state.

Technetium-99m red blood cell venography in upper extremity deep venous thrombosis

The efficacy of Tc-99m RBC venography has been demonstrated with respect to the study of lower extremity deep venous thrombosis. A case is presented where Tc-99m RBC venography was used to study the upper as well as lower extremities in a patient with upper extremity deep venous thrombosis (DVT) who was found to have pulmonary embolism.

Experimental autoimmune dacryoadenitis. II. Harderian gland disease in the rat

Experimental autoimmune dacryoadenitis was induced in 100% of Lewis rats by immunization with a KCl extract of Harderian gland in complete Freund's adjuvant (CFA), providing that the animals had received simultaneously i.v. injection of killed Bordetella pertussis. No significant pathological changes in the Harderian gland were observed in control animals immunized with KCl extracts of lacrimal or salivary glands. Gel filtration of the KCl extract on Sephacryl S-300 column yielded three protein fractions. Fraction II (MW = 50-100K) induced severe Harderian gland disease following a single injection of 2.0 mg protein in CFA plus pertussis. The initial lesions consisted of multiple focal infiltrates of mononuclear cells. Later, the inflammatory process assumed a more granulomatous form, with significant contribution by epithelioid and giant cells. In contrast, Lewis rats immunized with Harderian gland fractions I or III proteins, or with extracts of lacrimal or salivary gland, showed little or no inflammatory lesions. These data suggest that Harderian gland contains unique tissue-specific autoantigen(s) capable of inducing autoimmune granulomatous dacryoadenitis in the rat.

Experimental autoimmune dacryoadenitis. I. Lacrimal gland disease in the rat

Experimental autoimmune dacryoadenitis was produced in Lewis rats by immunization with a single intradermal administration of a 3M KCl extract of exorbital lacrimal gland in CFA, when enhanced by simultaneous i.v. injection of killed Bordetella pertussis. No significant lacrimal lesions were observed in control animals immunized with the extracts of Harderian or salivary glands. Gel filtration of the 3M KCl extract on Sephacryl S-300 column yielded three protein fractions. Only fraction III (MW = 10-55K) induced marked dacryoadenitis following a single injection of 2.0 mg protein in CFA plus pertussis. The infiltrates in the exorbital lacrimal lesions were first apparent around the ducts and associated vasculature. From this area, the infiltrates appeared to spread to the acini drained by these ducts, ultimately involving as much as 30-50% of the gland. The affected glands most commonly showed a diffuse nongranulomatous infiltrate of small lymphocytes, macrophages, and plasma cells; this was focal in nature, involving acinar atrophy and breakdown, and replaced the normal architecture in extreme cases. The Harderian and salivary glands were uninvolved in these animals, suggesting a restricted specificity of this response. Lewis rats immunized with exorbital lacrimal gland fractions I or II in CFA plus pertussis showed only minimal lesions, similar to controls receiving CFA and pertussis without antigen. These findings suggest that an autoantigen exists in the lacrimal gland of the rat that is capable of inducing a specific lymphoproliferative dacryoadenitis.