Comparison of the effects of papain n vitamin A on cartilage. I. The effects in rabbits

Proteases involved in cartilage matrix degradation in osteoarthritis

Osteoarthritis is a common joint disease for which there are currently no disease-modifying drugs available. Degradation of the cartilage extracellular matrix is a central feature of the disease and is widely thought to be mediated by proteinases that degrade structural components of the matrix, primarily aggrecan and collagen. Studies on transgenic mice have confirmed the central role of Adamalysin with Thrombospondin Motifs 5 (ADAMTS-5) in aggrecan degradation, and the collagenolytic matrix metalloproteinase MMP-13 in collagen degradation. This review discusses recent advances in current understanding of the mechanisms regulating expression of these key enzymes, as well as reviewing the roles of other proteinases in cartilage destruction. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Biochemical and Immunological Effects of Listeria monocytogenes Hemolysin

The biochemical and immunological effects of Listeria monocytogenes hemolysin in CD-1 mice were studied. Intraperitoneal injection of 256 complete hemolytic units (CHU) caused a twofold increase in plasma beta-glucuronidase levels but was not lethal. In contrast, 256 or more CHU caused 100% lethality in 4 to 5 min when administered intravenously. Intravenous administration of 50 CHU caused a 10- to 11-fold increase in plasma beta-glucuronidase levels and was lethal for a variable percentage of the animals. Carbon clearance experiments showed the phagocytic index to be depressed by relatively small amounts of intravenously administered hemolysin and suggested that hemolysin may function as a leucocidal agressin during listeric infection. Increased plasma levels of ornithine carbamyltransferase after intravenous injection of hemolysin indicated hepatocellular damage. Liver carbohydrate and blood glucose determinations on fasted mice showed a reduced gluconeogenic capability in hemolysin-treated animals. Mice immunized with purified hemolysin or live vaccine were more resistant to several of the toxic parameters studied. The data indicate that hemolysin is produced during listeric infection and is antigenic, but not necessarily a protective immunogen.

CHANGES IN CONNECTIVE TISSUE AND INTESTINE CAUSED BY VITAMIN A IN AMPHIBIA, AND THEIR ACCELERATION BY HYDROCORTISONE

In view of the theory that an excess of vitamin A causes release of cathepsins from intracellular lysosomes, hypervitaminosis A was induced orally in the larvae of Xenopus laevis. It was predicted that the tails of these amphibia would undergo resorption prior to metamorphosis, since the presence of abundant lysosomes, associated with measurable increases of catheptic activity, had previously been demonstrated in the resorbing tails of amphibia during metamorphosis. This prediction was confirmed; after 3 to 4 weeks of hypervitaminosis A, the tails of treated animals underwent partial resorption. Other transitory appendages, the rostral tentacles, collapsed after 2 weeks of treatment with an excess of vitamin A, an effect analogous to the collapse of rabbits' ears after intravenous papain. These effects were related to the loss of metachromatic extracellular material in these appendages. Excess of vitamin A caused kyphoscoliosis and prognathos in the larvae. The hypervitaminotic larvae always developed a mucinous diarrhea, which was associated with a remarkable overgrowth of metachromatic goblet cells of the intestine. The entire intestine of the treated animals was more advanced in development than that of control larvae at equivalent stages. All the effects of hypervitaminosis A were accelerated by the simultaneous administration of hydrocortisone. This was held to be due to liberation of vitamin A from hepatic stores by the steroid, and is in contrast to the retardation of hypervitaminosis A by hydrocortisone in vitro.

Lewis Thomas and droopy rabbit ears

In 1956, Lewis Thomas discovered that injecting rabbits with a plant protease called papain caused their ears to collapse. This experiment led to the identification of the endogenous proteases that cause the tissue destruction seen in diseases such as rheumatoid arthritis.

Retinoids and mammalian development

All vertebrate embryos require retinoic acid (RA) for fulfilment of the developmental program encoded in the genome. In mammals, maternal homeostatic mechanisms minimize variation of retinoid levels reaching the embryo. Retinol is transported as a complex with retinol-binding protein (RBP): transplacental transfer of retinol and its uptake by the embryonic tissues involves binding to an RBP receptor at the cell surface. Embryonic tissues in which this receptor is present also contain the retinol-binding protein CRBP I and the enzymes involved in RA synthesis; the same tissues are particularly vulnerable to vitamin A deficiency. In the nucleus, the RA signal is transduced by binding to a heterodimeric pair of retinoid receptors (RAR/RXR). In general, the receptors show functional plasticity, disruption of one RAR or RXR gene having minor or no effects on embryogenesis. However, genetic studies indicate that RXR alpha is essential for normal development of the heart and eye. Excess RA causes abnormalities of many systems; altered susceptibility to RA excess in mice lacking RAR gamma or RXR alpha suggests that the teratogenic signal is transduced through different receptors compared with physiological RA function in the same tissue.

The influence of hydrocortisone on the action of excess vitamin A on limb bone rudiments in culture

The effect of hydrocortisone has been studied in organ cultures of the cartilaginous long bone rudiments from 7-day chick embryos and of the well ossified limb bones from late fetal mice. In the chick rudiments, which grow rapidly in culture, the growth rate was much reduced by hydrocortisone, less intercellular material was formed, and the hypertrophic cells of the shaft were much smaller than in the controls in normal medium. In the late fetal mouse bones, which grow very little in culture, hydrocortisone had no obvious effect on growth but arrested resorption of the cartilage. These effects resemble those described by others in the skeleton of animals treated with cortisone or hydrocortisone. The influence of hydrocortisone on the response of the chick and mouse explants to excess vitamin A was investigated. In the presence of excess vitamin A, cartilage (chick, mouse) and bone (mouse) rapidly disintegrated, but when hydrocortisone also was added to the medium, this dissolution of the intercellular material was much retarded, though not suppressed. The retardative action of hydrocortisone on the changes produced by excess vitamin A in skeletal tissue in culture, contrasts sharply with the strongly additive effect of the two agents on the skeleton in the intact animal (Selye, 1958). It is suggested that this discrepancy between the results obtained in vitro and in vivo is probably due to systemic factors that operate in the body but are eliminated in organ cultures.

Comparison of the effects of papain and vitamin A on cartilage. II. The effects on organ cultures of embryonic skeletal tissue

The effects of papain protease and of vitamin A on explanted limb bone rudiments from 7- and 13-day chick embryos and fetal mice have been studied and compared. The incubation of cartilaginous rudiments from 7-day chick embryos in a solution containing papain and cysteine resulted in complete loss of the metachromasia of the cartilage matrix within 1 hour; explants treated in this fashion recovered normal metachromatic staining properties when grown in normal medium for 4 days. The incubation of 7-day chick cartilage rudiments in a solution containing papain without cysteine resulted in partial loss of metachromasia from cartilage within 1 hour; the addition of vitamin A to the solution did not enhance the effect of papain during this period. The addition of papain to the culture medium in which 7-day chick embryo cartilage rudiments were grown resulted in uniform loss of the metachromasia of the cartilage matrix; similar explants grown in the presence of excess vitamin A also showed loss of the metachromasia of cartilage, but certain regions of the cartilage were affected earlier and more severely than others. Changes in cartilage cells, including loss of glycogen, occurred when the rudiment was grown in medium containing excess vitamin A, but not when it was grown in the presence of papain. Bone rudiments from 13-day chick embryos showed changes in cartilage similar to those seen in 7-day chick embryo rudiments when grown in the presence of papain or of excess vitamin A; the existing bone was not affected under these conditions. When grown in the presence of papain or excess vitamin A, the cartilage of late fetal mouse bone underwent changes similar to those already described in chick embryo rudiments. In contrast to the chick embryo rudiments, those from the fetal mouse showed rapid resorption of bone when grown in the presence of excess vitamin A. Papain had no effect on bone from either source. The changes seen in cartilage of explants grown in the presence of vitamin A and papain together were greater than those seen with either agent alone. The changes seen in fetal mouse bone grown in the presence of vitamin A were not enhanced by the additional presence of papain. On the basis of these observations, it is suggested that the changes in cartilage seen in experimental hypervitaminosis A may be the result of activation of a proteolytic enzyme or enzymes with properties similar to papain.

Local disappearance of epiphyseal growth plates in rats with hypervitaminosis A

Epiphyseal growth plates of proximal tibiae in rats with high doses of vitamin A (V-A) were observed. Of 4 groups, each consisting of 5 rats, three groups were given V-A at doses, IU/100 g by body weight/day, of 50,000, 100,000, and 150,000, respectively. The other group rats were given no V-A (control). Rats were administered V-A for the 5 days from 4 weeks after birth and sacrificed at 12 weeks after birth. Three rats of the 150,000 IU group died during the period of observation. The decalcified sections were stained with hematoxylin-eosin or toluidine blue. In the ground sections, microradiography, backscattered electron imaging, and energy-dispersive X-ray microanalysis were performed. These observations suggest that the local disappearance of epiphyseal growth plates under high doses of V-A goes in the order of the increased doses through the process of (1) calcified cartilage areae appearing in the resting cell zone, (2) some of the calcified areae extending in the growth plate towards the diaphysial side, (3) bone tissue replacing the calcified areae, and (4) the local disappearing of the growth plate. Such a local disappearance may be formed in the stressed proximal regions of tibiae.

THE SUSCEPTIBILITY OF CHICK EMBRYO SKIN ORGAN CULTURES TO INFLUENZA VIRUS FOLLOWING EXCESS VITAMIN A

The conversion of chick embryonic epidermis to mucous epithelium by excess vitamin A in organ culture as reported by Fell and Mellanby (5) was shown to be accompanied by a corresponding change of susceptibility to influenza and vaccinia viruses. Untreated epidermis of 10- to 12-day chick embryos supported the growth of influenza (PR8) virus in organ cultures and a maximum infectivity (EID(50)) titer was reached 2 to 3 days after infection. At the same time) the epidermis showed squamous keratinization, beginning about the 4th day of cultivation. Addition of excess vitamin A (40 microg per ml) to the skin organ culture induced the following changes: (a) mucous metaplasia of the epidermis which was usually first evident after 4 to 5 days in the vitamin A medium, (b) increase in the daily and maximum yield of influenza virus, if the epidermis had been grown for 4 or more days in the vitamin A medium before infection took place, and (c) decrease in the production of vaccinia virus under similar conditions. The maximum yield of both viruses remained unchanged, however, if excess vitamin A was introduced to the organ culture at the time of virus inoculation. The magnitude of increase in the yield of influenza virus in this organ culture system was found to be proportionally related to the concentration of vitamin A added 4 or more days before inoculation of this virus. Increasing doses of vitamin A however, had no effect on the short-term growth of influenza virus in tissue cultures of chorio-allantoic membrane. Observation on the early period (2 to 12 hours) of influenza virus growth initiated in the 4-day organ cultures of chick embryonic skin showed no significant difference in virus production between the normal and the vitamin A medium groups. The change of virus specificity apparently is not due to the presence of excess vitamin A per se, but appears to be related to the change of differentiation produced in the organ culture system.

STUDIES ON LYSOSOMES. III. THE EFFECTS OF STREPTOLYSINS O AND S ON THE RELEASE OF ACID HYDROLASES FROM A GRANULAR FRACTION OF RABBIT LIVER

Streptolysins O and S from hemolytic streptococci have been added to granular fractions of tissue homogenates in 0.25 M sucrose prepared from rabbit liver, heart, spleen and lymph nodes. At concentrations ranging from 0.65 microg/ml to 2.0 mg/ml of streptolysin S, and from 10 microg/ml to 1.0 mg/ml of streptolysin O, two lysosomal enzymes (beta glucuronidase and acid phosphatase) and, to a lesser degree, one mitochondrial enzyme (malic dehydrogenase) were released into the supernatants of the reaction mixture. Although the hemolytic action of each lysin paralleled the effect on lysosomes, at equivalent levels of hemolytic activity, SLS was approximately 10 times more active on lysosomes than SLO. SLO was inhibited by cholesterol, cortisol, and specific antibody in vitro; pretreatment of animals with cortisone decreased the susceptibility of their isolated lysosomes to SLO. These agents failed to prevent SLS action on lysosomes. SLO had a pH optimum of 6.5 against lysosomes while SLS was maximally active at 7.5. No other streptococcal extracellular products were as active on lysosomes as the streptolysins, although activated streptococcal proteinase precursor released some hydrolases from the granules. Similarities between the actions of SLO and SLS on red cells and lysosomes suggested that the membranes bounding lysosomes and erythrocytes have common properties.

THE EFFECTS OF PAPAIN, VITAMIN A, AND CORTISONE ON CARTILAGE MATRIX IN VIVO

The extreme and, apparently, selective vulnerability of chondromucoprotein in cartilage matrix to the action of proteolytic enzymes in vivo provides a useful model for studying factors involved in the transport, inhibition, and activation of a protease, papain, in the blood and tissues. The lysis of cartilage matrix which occurs in hypervitaminosis A is the result of release, probably from chondrocytes, of cathepsins normally contained within lysosomes. Cortisone possesses two properties which are not only of importance for this experimental model but also may have more general bearing on the physiological functions of this hormone with respect to connective tissue. One property is to prevent the resynthesis or deposition of chondroitin sulfate in cartilage matrix, after depletion of the latter. The other, which may be relevant to the "anti-inflammatory" actions of cortisone, is to increase the stability of lysosomes and prevent release of the acid hydrolytic enzymes contained in these organelles.

Inhibition of cartilage proteoglycan release by a specific inactivator of cathepsin B and an inhibitor of matrix metalloproteinases. Evidence for two converging pathways of chondrocyte-mediated proteoglycan degradation

OBJECTIVE

To investigate mechanisms of cartilage matrix destruction by a study of the effects of a specific inactivator of cathepsin B and an inhibitor of several matrix metalloproteinases (MMP) on cartilage proteoglycan release.

METHODS

Cartilage explants were treated with either recombinant human interleukin-1 alpha (rHuIL-1 alpha) or retinoic acid in the presence or absence of the inhibitors, and proteoglycan release was quantitated. Tests for nonspecific effects of the inhibitors included reversibility, rates of protein synthesis and glycolysis, and effects on other rHuIL-1 alpha-mediated events.

RESULTS

The cathepsin B inactivator inhibited rHuIL-1 alpha-stimulated proteoglycan release at nanomolar concentrations, but failed to significantly inhibit retinoic acid-stimulated proteoglycan release. An inhibitor of MMP was inhibitory to both rHuIL-1 alpha-stimulated release and retinoic acid-stimulated release.

CONCLUSION

Cathepsin B is implicated in rHuIL-1 alpha-stimulated loss of cartilage proteoglycan. Its lack of involvement in retinoic acid-stimulated proteoglycan release suggests the existence of at least 2 pathways of cartilage proteoglycan breakdown, which may converge at the activation of a matrix prometalloproteinase.

The secretion of the tissue inhibitor of metalloproteinases (TIMP) by human synovial fibroblasts is modulated by all-trans-retinoic acid

The matrix metalloproteinases are a family of enzymes involved in the turnover of the connective tissues. The regulation of these enzymes is complex, involving the control of synthesis, the activation of proenzyme forms and the presence of specific inhibitors. Retinoids have been reported to inhibit the production of metalloproteinases by human and rabbit synovial fibroblasts and by human skin fibroblasts. The production of the highly specific tissue inhibitor of metalloproteinases (TIMP) by connective tissue cells may be crucial in the regulation of connective tissue breakdown and this present study was undertaken to determine if retinoic acid (RA) could modulate TIMP and collagenase production by synovial fibroblasts. The results show that RA at concentrations from 10(-7) to 10(-5) M significantly stimulated the secretion of TIMP by two of three human synovial cell lines. The effect of mononuclear cell factor (MCF) on TIMP and collagenase levels was also investigated. The apparent reduction of collagenase levels in the presence of RA, could result from a failure to accurately measure this enzyme in the presence of increased levels of TIMP.

Transforming growth factor beta stimulates urokinase-type plasminogen activator and DNA synthesis, but not prostaglandin E2 production, in human synovial fibroblasts

Transforming growth factor beta (TGF-beta) is usually associated with matrix formation and tissue repair; in contrast, cellular expression of the serine proteinase, urokinase-type plasminogen activator (u-PA) is often correlated with tissue remodeling, as well as with cell migration and transformation. We report here that purified recombinant human TGF-beta (greater than or equal to 300 pg/ml) can stimulate rapidly (within 2 h) the u-PA activity of nonrheumatoid synovial fibroblast-like cells. As for interleukin 1 (IL-1), u-PA mRNA levels are raised in response to TGF-beta, but unlike IL-1, no increase in prostaglandin E2 levels occurs. In contrast to a number of other examples in the literature, in which these two cytokines have opposing actions, TGF-beta can potentiate the action of optimal concentrations of IL-1 in enhancing u-PA expression. These effects of TGF-beta are similar to those of all-trans-retinoic acid. In addition, synovial fibroblast DNA synthesis was stimulated by TGF-beta. Because TGF-beta has been detected in the synovia of patients with rheumatoid arthritis and has been shown to reduce the collagenase levels and proliferation of synovial fibroblast-like cells, it has been proposed by others to be involved beneficially in the reparative processes occurring in arthritic lesions. However, on the basis of our findings, we propose alternative functions for this cytokine--namely, roles in the destructive events as well as in the synovial hyperplasia observed in rheumatoid joints.

Magnetic resonance imaging reflects cartilage proteoglycan degradation in the rabbit knee

Cartilage degeneration in osteoarthritis is initiated by a loss of proteoglycan. Intra-articular injection of papain causes a reversible loss of proteoglycan in rabbit knees. Rabbits were scanned with magnetic resonance imaging (MRI), using a 1.5T Signa superconducting magnet with 3 inch surface coil. Spin echo sequences were performed in the coronal and sagittal planes at 0, 24, 48, and 72 h after intra-articular injection of papain to obtain T1, proton density, and T2-weighted images. Cartilage proteoglycan content was measured biochemically and histochemically. Reduced articular cartilage thickness in the MR images of papain-treated knees corresponded to changes in cartilage proteoglycan content.

Transplacental effects of vitamin A on fetal bones in mice--follow-up studies on postnatal recovery

Pregnant mice were injected with pharmacological doses of vitamin A during days 11-19 of gestation with the purpose of studying the long bones of offspring up to the age of 1 week. Tibiae were collected for routine light microscopic examination and tranmission electron microscopic examination. In addition, biochemical studies were conducted to determine the calcium, phosphorus, and magnesium content as well as the hydroxyproline and protein content of the bones. Treatment with vitamin A resulted in reduced weight and length of the long bones, as well as the presence of excessive calcification throughout the hypertrophic zone of the cartilaginous epiphyses. Matrix vesicles, many of them containing hydroxyapatite crystals, were observed and found to be distributed within the cartilaginous epiphyses in a similar pattern as in untreated control mice offspring, but mineral crystals were also observed unassociated with the matrix vesicles. The calcium, phosphate, magnesium, and hydroxyproline content was reduced in the vitamin A offspring. However, the percentage of these minerals expressed per dry weight bone was higher than in controls, verifying the morphological findings that although vitamin A inhibits bone growth, it enhances calcification in the growth plate.

The Histologic Effect of Hypervitaminosis A on Laryngeal Cartilages

This study investigated the role of hypervitaminosis A on the developing larynx. Pregnant rats received a dose of 100,000 units of Vitamin A on either Day 8 or Day 11 of gestation. The hyaline laryngeal cartilages of the neonatal rats were studied. The cricoid and arytenoid cartilages appeared to be the most affected. There was a pronounced central disorganization of the structure of the cartilage, with numerous swollen lacunae devoid of chondrocytes. The thyroid cartilage was the least affected. The center of the cartilage displayed a minimal amount of disorganization, when compared to the control. The effect of hypervitaminosis A on cartilaginous tissue is discussed, as well as its possiible effect on the development of laryngeal cartilages.

The application of quantitative cytochemistry to the study of diseases of the connective tissues

The connective tissues are a complex organisation of tissues, cells and intercellular materials spread throughout the body and are subject to a large number of diseases. Such complexity makes the study of the metabolism of the connective tissues in health and more particularly in disease states difficult if one uses conventional biochemical methodology. Fortunately the techniques of quantitative cytochemistry, as developed in recent years, have made it possible to study the metabolism of even such complex and refractory connective tissues as bone. Using properly validated assays of enzyme activity in unfixed sections from various tissues a number of the diseases of the connective tissues have been studied. For example the synovia from patients with rheumatoid arthritis and related conditions have been studied using these techniques and marked alterations in the metabolism of the synovial lining cell population of this tissue have been demonstrated. These alterations in metabolism are believed to be related to the destruction of cartilage and bone found in such diseases. Investigations of the metabolism of the chondrocytes of articular cartilage in a strain of mice which spontaneously develops osteoarthritis has revealed a lack of certain key enzymes of carbohydrate metabolism in precisely those areas where degradation of the matrix of articular cartilage begins suggesting a causal relationship between these events. These same techniques have been used to study the cellular kinetics and metabolism of the dermis and epidermis in the disfiguring disease, psoriasis. The metabolism of healing bone fractures, the diagnosis and treatment of the mucopolysaccharidoses and the metabolic effects of currently used anti-inflammatory and anti-rheumatic drugs have also been examined. Perhaps the most exciting aspect of these studies has been the development and use of the technique of the cytochemical bioassay (CBA) to study hormonally mediated diseases of the connective tissues. Such studies have recently shed new light on the molecular lesion in pseudohypoparathyroidism. Though still in their relative infancy the studies described in this review show the potential inherent in the use of quantitative cytochemistry for the study of diseases of the connective tissues.

Stimulation of the plasminogen activator activity of human synovial fibroblasts by retinoids

Nonrheumatoid human synovial fibroblasts in culture, while having low basal plasminogen activator levels, were stimulated to produce much more of this protease activity by low concentrations of a series of retinoids. The most potent retinoid tested, all-trans retinoic acid, was active over the range 10(-11)-10(-6)M. The increased plasminogen activator activity in the presence of 10(-6)M retinoic acid was first observed within 40 minutes under appropriate experimental conditions, required RNA and protein synthesis, and was reversible after short incubation periods. This stimulation was suppressed by low concentrations of antiinflammatory glucocorticoids such as dexamethasone.

The effects of retinoids on neutrophil functions in vitro

Vitamin A (retinol) and its analogues (retinoids) are clinically effective in cystic acne and psoriasis, diseases in which neutrophils may constitute major components of inflammatory cell infiltrates. We found that the earliest histopathologic alteration in psoriasis is the disappearance of neutrophils at 2 to 4 weeks after the initiation of therapy with etretinate. Since retinoids may exert anti-inflammatory effects by virtue of an action upon neutrophils, we studied the effects of the following retinoids on discrete neutrophil functions in vitro: retinol, retinyl acetate, retinal, tretinoin, isotretinoin, etretinate, and Ro 10-1670. Although they had no significant effects upon aggregation, chemokinesis, or chemotaxis, all of the retinoids, with the exception of etretinate and Ro 10-1670, profoundly inhibited superoxide anion production and lysosomal enzyme release. Tretinoin and isotretinoin were the most effective inhibitors. We propose that these drugs exert their pharmacologic effects (resolution of inflammatory lesions) by inhibiting the release of mediators of inflammation and by preventing the accumulation of neutrophils in acne lesions when applied topically or systemically, respectively.

The effect of hypervitaminosis A on rat palatal development

Retinoic acid or retinyl acetate was administered to pregnant rats in doses sufficient to induce a 90% incidence of cleft palate. In another study, a delay in the reorientation of the palatal shelves was observed to be longer with the more potent teratogen, retinoic acid. On day 16 of gestation, 24 hours after final dosage with vitamin A, the synthesis of DNA and protein was studied in fetal carcass, mandible, and palate, and that of sulfated mucopolysaccharides (S-MPS) and glycoproteins (GP) in fetal head, mandible, and palate. Increases in DNA synthesis in fetal palate and in GP synthesis in fetal palate were found; thus, the mechanism of action of vitamin A in inducing cleft palates in rats may be caused by interference with the normal biochemical synthetic pattern of the palatal shelves.

Effect of vitamin A and methylprednisolone on canine prostate in organ culture

Organ explants from the canine prostate with and without methylprednisolone pretreatment were cultivated for ten days in Trowell's T-8 medium or medium supplemented with testosterone and/or vitamin A. Upon termination of the experiments, explants were fixed and examined histologically. All glands from the most central section of each explant were graded according to epithelial type, and from these grades the proportion of acini with maintained columnar cells was calculated for each explant. Stromal cellular maintenance was also estimated. While a small proportion of explants from the vitamin-treated and methylprednisolone-pretreated groups showed epithelial maintenance, a combination of these treatments significantly increased such maintenance. Stromal maintenance was enhanced with methylprednisolone pretreatment but not by vitamin A. These results are in accord with the hypothesis that methylprednisolone acts to stabilize the lysosomal membrane, thus protecting tissue against the effects of ischemic shock. In protected explants vitamin A is able to maintain a columnar glandular epithelium. In a subsequent experiment a series of linoleic acid dosages was tested in the presence or absence of vitamin A. In neither case was this fatty acid of value in improving epithelial or stromal maintenance.

Virus-induced lysosomal enzyme dissolution of nasal turbinate cartilage

The mechanism of laryngotracheitis virus-induced dissolution of chick nasal turbinate cartilage was studied by lysosomal enzyme histochemistry. Five-day-old chicks were infected by intranasal instillation, and changes in lysosomal enzyme distribution were followed at daily intervals through the tissue regeneration stage, Day 28. In the mucosa the lysosomes were activated beginning on Day 1, and glycerol acid phosphatase and a diffuse form of beta-glucuronidase were released concomitant with tissue cell destruction. In the chondrocytes (where glycerol acid phosphatase was absent), beginning on Day 2, particulate (lysosomal) beta-glucuronidase decreased as diffuse beta-glucuronidase increased and extended out into the matrix. The cartilage lost its metachromatic staining properties and became soft and pliable. Regeneration of the mucosa started on Day 6 and gradual reappearance of metachromatic staining of the cartilage began on Day 8 with considerable recovery of original turbinate structure by Day 12. A lysosomal membrane labilizer, vitamin A, exacerbated the cartilage pathology, whereas a stabilizer, cortisone, retarded it.

A unifying concept for the role of matrix vesicles and lysosomes in the formal pathogenesis of diseases of connective tissues and blood vessels

The cells of the connective tissues contain lysosomes with enzymes capable of degrading intercellular substances (collagen, elastin, proteoglycans) and release their enzymes in membrane-bound or in free form into their intercellular substance. In this way extracellularly located lysosomes (= matrix lysosomes) can be detected by morphological and enzymatic means as well as by their metal concentrating property. This function of such matrix-lysosomes is in connection with the two step-degradation of the connective tissue and is thought to be the main part for the fibrocytic fibrolysis, chondrocytic chondrolysis, osteocytic osteolysis and myocytic mediolyses in the vessel wall. The cells of the mesenchymal tissues thus control the turnover and transformation of their own ground substance. Inflammatory and immunologic processes are suggested to be superimposed on this lysosomal action. If the lysosomal enzyme system in the connective tissues and the vessel wall gets out of control, the consequences can be dangerous as e.g. in case of relapsing polychondritis and arterial aneurysms. In this enzyme system proteolytic activators as well as proteolytic decomposable inhibitors are present. The corresponding proteolytic processes are of lysosomal nature and are subordinated to other regulatory mechanisms.

Glucocorticosteroid inhibition of nonphagocytic discharge of lysosomal enzymes from human neutrophils

Glucocorticosteroids and mineralocorticosteroids were tested for their capacity to inhibit the nonphagocytic discharge of two lysosomal enzymes--a cartilage matrix-degrading neutral protease and beta-glucuronidase--from highly purified human neutrophils. Lysosomal enzyme discharge from neutrophils adherent to nonphagocytizable, immobilized, heat-aggregated IgG was inhibited by the four glucocorticosteroids--methylprednisolone sodium succinate, triamcinolone acetonide hemisuccinate, para methasone acetate, and hydrocortisone sodium succinate. These glucocorticoids also inhibited zymosan-induced release of beta-glucuronidase from neutrophils that had been pretreated with cytochalasin B in order to completely prevent the onset of phagocytosis. Inhibition by the glucocorticoids of lysosomal enzyme discharge provoked by a soluble divalent cation ionophore was also observed. Neither desoxycorticosterone acetate nor aldosterone hemisuccinate, two mineralocorticosteroids, inhibited lysosomal enzyme release. Similarly, the salt moieties of some of the steroids tested, such as sodium succinate and sodium acetate, failed to elicit an effect on enzyme release. Therefore interference with lysosomal enzyme discharge was restricted to the glucocorticosteroid ring structure. Because interference either with the adherence of neutrophils to immune reactants or with the activities of the discharged lysosomal enzymes by the glucocorticoids could be interpreted as inhibition of lysosomal enzyme release, steroidal effects on these parameters were examined. None of the glucocorticoids tested elicited any significant effects on neutrophil adherence or lysosomal enzyme activity. Thus it appears that glucocorticosteroids are capable of inhibiting directly the nonphagocytic discharge of lysosomal enzymes from human neutrophils.

The effect of complement-sufficient antiserum against pig erythrocytes on pig articular tissues in organ culture

Pig cartilage devoid of marrow or synovium is virtually unaffected by rabbit complement-sufficient antiserum to pig erythrocytes (AS + C'), probably because normal cartilage matrix excludes immunoglobulins. When synovium or invading marrow is present, AS + C' causes depletion of the proteoglycan, with consequent entry of IgG into the cartilage, followed by the breakdown of collagen; the chondrocytes assume a fibroblastic form and their reaction with the antiserum is greatly reduced. If degradation of the matrix has not advanced too far, new matrix is regenerated when the explant is transferred to control medium. Experiments on the depletion of pure cartilage by exposure to retinol, indicate that articular cartilage produces enzymes capable of degrading protoglycan but not collagen. The work was done in collaboration with colleagues at the Strangeways Laboratory and in the Division of Immunology, Pathology Department, University of Cambridge.

Relapsing polychondritis: review of current status and case report,

This communication has attempted to review the present state of published knowledge on the syndrome of relapsing polychondritis. Basic anatomic, physiologic, and biochemical changes in this disorder are summarized and the role of metabolic and immunologic alterations in the pathogenesis discussed. An additional case of relapsing polychondritis is reported, and the clinical features of this case, plus those of 131 previously reported, are reviewed with discussion of present day therapeutic experience and prognosis.

Actions of vitamins A and E and some nicotinic acid derivatives on plasma lipids and on lipid infiltration of aorta in cholesterol-fed rabbits

Marked hypercholesterolemia and moderate lipid infiltration of the aorta were induced by feeding rabbits a diet containing 1% cholesterol + 3% corn oil for 70 days. In the liver the concentration and pool size of cholesterol increased and those of triglycerides (TG) decreased. On dietary addition of vitamin A and vitamin E (44 000 I.U. and 125 mg respectively, once daily for 5 days a week) the following changes were noted in comparison with the fat-fed rabbits not receiving extra addition of vitamins. There was a slight decrease of the levels of plasma cholesterol and an increase of those of plasma TG. The liver cholesterol concentration increased but, according to the concomitant reduction of the liver weight, there was no significant change in lever cholesterol or TG pools. In the aorta the vitamins markedly reduced the lipid infiltrated area as well as the cholesterol content. Both niceritrol** and S-2040 [pyridine-2,5-dicarboxylic acid di(beta-pyridylcarbinol ester)] in a dietary concentration of 0.5% decreased plasma cholesterol by about 20%. This reduction, as well as that induced by the vitamins, was confined to the VLDL-fractions only. S-2040 slightly reduced the cholesterol accumulation in the aorta. In rabbits given both the vitamins and niceritrol or S-2042 there was an additive reduction of plasma cholesterol. Here the nicotinic acid derivatives were partly able to counteract the increases of plasma TG induced by the vitamins. In the aorta the combination vitamins + S-2042 but not that of vitamins + niceritrol tended to give a better protection than the vitamins alone. On a normal diet vitamins A + E significantly increased the liver cholesterol concentration and pool and decreased the liver TG pool, but did not affect the other parameters. Possible mechanisms for the prophylactic action of the vitamins against lipid infiltration of the aorta of cholesterol-fed rabbits are discussed.