Production of collagenase by mouse peritoneal macrophages in vitro. Characterization of sites of cleavage of tropocollagen

Interaction between macrophages and articular surfaces: an in vitro transmission and scanning electron microscopy study

Interactions between macrophages and articular surfaces were studied in an in vitro model which has been described before. Either stimulated peritoneal macrophages or a purified population of bone marrow macrophages were incubated with mice femoral heads which were either untreated or were digested with collagenase, trypsin or hyaluronidase prior to incubation. Scanning electron microscopy (EM) examination showed that macrophages attached to the surface and in their vicinity tags and fibers were visible. Transmission EM was used after labeling the surfaces with cationized ferritin employed as a sensitive marker to define the integrity of the articular surface. Alterations of the surface of various degrees of intensity were seen in all the sections examined. No adhering macrophages were found, due probably to detachment of cells during tissue processing for transmission EM. Attachment of macrophages to the surface and alterations of the latter were seen also when hyaluronic acid was added to the incubation medium or when the surfaces had been treated with hyaluronidase before incubation.

Involvement of prostaglandin E and adenosine 3', 5'-monophosphate in lipopolysaccharide-stimulated collagenase release by rat Kupffer cells

Kupffer cells exposed to bacterial lipopolysaccharide in vitro synthesized collagenase and released the major portion of it into the extracellular space while the intracellular level of enzyme was not altered significantly. Cycloheximide prevented the appearance of collagenase in the medium indicating de novo synthesis. Indomethacin, an inhibitor of cyclooxygenase, also blocked collagenase synthesis. In line with this observation. Kupffer cells were found to synthesize substantial amounts of prostaglandin E2 when exposed to lipopolysaccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimulated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3', 5'-monophosphate as well as of prostaglandin E2 or, to a lesser extent, prostaglandin E1 allowed indomethacin-inhibited cells to resume the production of collagenase. It is proposed that in rat Kupffer cells lipopolysaccharide-elicited collagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels.

Connective tissue components of the normal and fibrotic liver. I. Structure, local distribution and metabolism of connective tissue components in the normal liver and changes in chronic liver diseases

The first part of this review describes the chemistry, the occurrence and the metabolism of extracellular connective tissue components in the liver. The normal liver contains typical connective tissue proteins (collagens, structural glycoproteins and proteoglycans) not only in vessel walls, perivascular areas and in the capsule, but they occur also in small amounts in the parenchyma, mainly in the space of Disse along the sinusoidal walls. The "interstitial" collagens type I and III represent the major amount of collagen in the normal as well as in fibrotic liver, showing a relative increase of type III in fibrosis. Basement membrane collagens type IV and V as well as the cysteine-rich collagenous components "7 S collagen" and "short chain collagen" have been shown to occur in extracts prepared after limited pepsin digestion. In the normal liver, basement membrane collagen can hardly be detected within the parenchyma by immunofluorescence microscopy; increased occurrence, however, can be shown along the sinusoids even in early stages of chronic liver diseases. The glycoprotein fibronectin was shown to be distributed very similarly to collagens type I and III, whereas the basement membrane specific glycoprotein laminin is restricted to vessel walls and the epithelial layer of bile ductuli in the normal liver but is also found in the parenchyma in fibrosis. Occurrence of proteoglycans is increased in fibrosis: a change in the composition of glycosaminoglycans from mainly heparan sulfate in the normal to dermatan- and chondroitin sulfate in the fibrotic liver was observed. It is not yet clear which cell type is mainly responsible for increased connective tissue synthesis in fibrosis. The occurrence of cells resembling smooth muscle cells ("myofibroblasts") in connective tissue septa of fibrotic livers and the fact that similar cells which actively synthesize collagen grow from explants of fibrotic livers may indicate the significance of this cell type in the process of liver fibrosis.

Vitreous membrane formation after experimental vitreous haemorrhage

The formation of vitreous membranes after intravitreal haemorrhage was studied in rabbit eyes. Early detachment of the posterior vitreous was followed by the formation of large cellular membranes, composed of aggregated giant macrophages within fine collagen sheets. Progressive reabsorption of the cellular material resulted in acellular membranes composed of endogenous vitreous collagen. Fibroblastic activity was not observed, and it was considered that the vitreous body, particularly its hyaluronic acid component, may present a barrier to the invasion of fibroblasts and other cells during the resolution of vitreous clots.

Neutral proteinases secreted by macrophages degrade basic protein: a possible mechanism of inflammatory demyelination

In the inflammatory demyelinating diseases, such as multiple sclerosis, Landry-Guillain-Barré syndrome and experimental allergic encephalomyelitis, demyelination occurs in the vicinity of infiltrating mononuclear cells. Although the histopathology is characteristic of each disease, the general observation that myelin destruction in inflammatory lesions begins prior to phagocytosis suggests a common mechanism for myelinolysis in these diseases. Recent studies show that stimulated macrophages secrete several neutral proteinases, including plasminogen (Plg) activator. We have tested the possibility that these proteinases could, directly or indirectly, initiate myelin destruction. Isolated brain myelin was incubated with supernatant media from cultures of stimulated mouse peritoneal macrophages in the presence and absence of Plg. Cell supernatants alone caused some degradation of basic protein (BP) in myelin. The amount degraded was considerably enhanced in the presence of Plg. The other myelin proteins remained essentially intact. While the Plg-independent proteolytic activity in the supernatants was abolished by EDTA, known to inhibit the neutral proteinases, the Plg-dependent hydrolysis was inhibited by p-nitrophenylguanidinobenzoate, an inhibitor of Plg activator and plasmin. These results suggested that the Plg activator secreted by the macrophages generated plasmin, which selectively degraded BP. This interpretation was confirmed by the observation that urokinase, a Plg activator, plus Plg was effective in degrading BP in myelin. We propose that the action of neutral proteinases released by stimulated macrophages, and its amplification by the Plg-plasmin system, may play a significant role in several inflammatory demyelinating diseases; and that the relative specificity of these reactions for myelin lies in the extreme susceptibility of BP to proteolysis.