John R. Harper

Antifibrotic effect of decorin in a bleomycin hamster model of lung fibrosis

We reported previously that treatment with antibody to transforming growth factor-beta (TGF-beta) caused a marked attenuation of bleomycin (BL)-induced lung fibrosis (LF) in mice. Decorin (DC), a proteoglycan, binds TGF-beta and thereby down-regulates all of its biological activities. In the present study, we evaluated the antifibrotic potential of DC in a three-dose BL-hamster model of lung fibrosis. Hamsters were placed in the following groups: (1) saline (SA) + phosphate-buffered saline (PBS) (SA + PBS); (2) SA + DC; (3) BL + PBS; and (4) BL + DC. Under pentobarbital anesthesia, SA (4 mL/kg) or BL was instilled intratracheally in three consecutive doses (2.5, 2.0, 1.5 units/kg/4 mL) at weekly intervals. DC (1 mg/mL) or PBS was instilled intratracheally in 0.4 mL/hamster on days 3 and 5 following instillation of each dose of SA or BL. In week 4, hamsters received three doses of either DC or PBS every other day. The hamsters were killed at 30 days following the first instillation, and their lungs were appropriately processed. Lung hydroxyproline levels in SA + PBS, SA + DC, BL + PBS, and BL + DC groups were 965, 829, 1854, and 1387 microg/lung, respectively. Prolyl hydroxylase activities were 103, 289, and 193% of SA + PBS control in SA + DC, BL + PBS, and BL + DC groups, respectively. The myeloperoxidase activities in the corresponding groups were 222, 890, and 274% of control (0.525 units/lung). Intratracheal instillation of BL caused significant increases in these biochemical markers, and instillation of DC diminished these increases in the BL + DC group. DC treatment also caused a significant reduction in the infiltration of neutrophils in the bronchoalveolar lavage fluid (BALF) of hamsters in the BL + DC group. However, DC treatment had little effect on BL-induced increases in lung superoxide dismutase activity and lipid peroxidation and leakage of plasma proteins in the BALF of the BL + DC group. Hamsters in the BL + PBS group showed severe multifocal fibrosis and accumulation of mononuclear inflammatory cells and granulocytes. In contrast, hamsters in the BL + DC group showed mild multifocal septal thickening with aggregations of mononuclear inflammatory cells. Hamsters in both control groups (SA + PBS and SA + DC) showed normal lung structure. Frozen lung sections following immunohistochemical staining revealed an intense staining for EDA-fibronectin and collagen type I in the BL + PBS group as compared with all other groups. It was concluded that DC potentially offers a novel pharmacological intervention that may be useful in treating pulmonary fibrosis.

In vivo interactions of TGF-β and extracellular matrix

TGF-beta, a multifunctional cytokine, plays an important role in embryogenesis and in regulating repair and remodeling following tissue injury. Many of the biological actions of TGF-beta are mediated by widespread effects on deposition of extracellular matrix. TGF-beta stimulates the synthesis of individual matrix components including proteoglycans, collagens and glycoproteins. TGF-beta also blocks matrix degradation by decreasing the synthesis of proteases and increasing the synthesis of protease inhibitors. Finally, TGF-beta increases the synthesis of matrix receptors and alters their relative proportions on the surface of cells in a manner that could facilitate adhesion to matrix. All of these events have largely been demonstrated in vitro in cultured cells. In an experimental model of glomerulonephritis we have shown that TGF-beta is responsible for the accumulation of pathological matrix in the glomeruli following immunological injury. Furthermore, all three of TGF-betas actions on extracellular matrix--increased synthesis, decreased degradation and modulation of receptors--have now been documented to be involved in matrix deposition in vivo in this model. Administration of the proteoglycan decorin suppressed TGF-beta-induced matrix deposition in the nephritic glomeruli, thus confirming a physiological role for decorin as a regulator of TGF-beta. Inhibitors of TGF-beta may be important future drugs in treating fibrotic diseases caused by overproduction of TGF-beta.

Myelin-Associated Glycoprotein Shares an Antigenic Determinant with a Glycoprotein of Human Melanoma Cells

Abstract A sulfated 100K‐dalton glycoprotein has been shown to be released into the culture medium of melanoma cells. Monoclonal antibodies 10C5 and 11B5, which were raised to human melanoma cells, as well as HNK‐1 bind to this glycoprotein. It is shown here that mouse anti‐myelin‐associated glycoprotein (MAG) carbohydrate antibodies raised to human MAG and a human IgM paraprotein associated with neuropathy also bind to the same 100K molecule. However, anti‐MAG antibodies recognizing peptide epitopes do not appear to react with this glycoprotein of melanoma cells, a result suggesting that its similarity to MAG is restricted to shared carbohydrate moieties. The anti‐melanoma antibodies (10C5 and 11B5) resemble HNK‐1 in binding to MAG and to some 19–28K‐dalton glycoproteins and sulfated, glucuronic acid‐containing sphingoglycolipids of the peripheral nervous system (PNS). In addition, the anti‐melanoma antibodies cross‐react with neural cell adhesion molecule (N‐CAM), an observation emphasizing the shared antigenicity between MAG and other adhesion molecules. The results demonstrate that the anti‐melanoma antibodies fall into a class of monoclonal antibodies (including HNK‐1, human IgM paraproteins associated with neuropathy, anti‐human MAG antibodies, and L2 antibodies) that are characterized by reactivity against related carbohydrate determinants shared by human MAG, N‐CAM, and several protein and lipid glyco‐conjugates of the PNS.

ISOLATION AND SEQUENCE OF PARTIAL CDNA CLONES OF HUMAN L1 : HOMOLOGY OF HUMAN AND RODENT L1 IN THE CYTOPLASMIC REGION

Abstract: We have isolated cDNA clones coding for the human homologue of the neuronal cell adhesion molecule L1. The nucleotide sequence of the cDNA clones and the deduced primary amino acid sequence of the carboxy terminal portion of the human L1 are homologous to the corresponding sequences of mouse L1 and rat NILE glycoprotein, with an especially high sequence identity in the cytoplasmic regions of the proteins. There is also protein sequence homology with the cytoplasmic region of the Drosophila cell adhesion molecule, neuroglian. The conservation of the cytoplasmic domain argues for an important functional role for this portion of the molecule.

Human Neuroectoderm-Derived Cell Line Secretes Fibronectin that Shares the HNK-1/10C5 Carbohydrate Epitope with Neural Cell Adhesion Molecules

A human malignant melanoma cell line, Melur, secretes several glycoproteins that contain a unique carbohydrate epitope shared by neural cell adhesion molecules and recognized by the monoclonal antibodies HNK‐1, L2, and 10C5. In this report, we present evidence that one of the major melanoma glycoproteins containing the HNK‐1/10C5 epitope is the cell adhesion molecule, fibronectin, or a fibronectin‐like molecule. Melanoma‐derived fibronectin was isolated from serum‐free conditioned medium by gelatin‐Sepharose affinity adsorption and shown to react with monoclonal antibodies HNK‐1 and 10C5 in Western blot analysis. HNK‐1‐containing fibronectin was purified on a gelatin‐Sepharose column followed by an affinity column using a monoclonal antibody against the HNK‐1 carbohydrate. The purified HNK‐1‐fibronectin then could be incorporated into the extracellular matrix of hamster fibroblasts in vitro, and such a matrix was detectable using the HNK‐1 monoclonal antibody in an immunofluorescence assay. Of the seven neuroectoderm‐derived tumor cell lines tested, only the Melur melanoma cell secreted fibronectin containing the HNK‐1 carbohydrate. Identification of human neuroectoderm‐derived fibronectin as a potential carrier of the HNK‐1 carbohydrate suggests a new role for fibronectin in neural development and regeneration, and represents a new model for studying the function of this carbohydrate domain in neural cell adhesion.

Antigenic Expression of Human Melanoma Cells in Serum-Free Medium

A human melanoma cell line, M14 , adapted to grow in serum free synthetic media was examined for its expression and secretion of several serologically defined melanoma associated antigens (MAA) previously described in this laboratory. Melanoma associated antigen expression and secretion was identical to that of M14 cells grown in parallel in serum supplemented medium. Spent synthetic media was found to be an enriched serum free source for the initial isolation of 100 kilodalton secreted glycoprotein MAA. M14 melanoma cells grown in synthetic media were also shown to be adaptable to the double agar clonogenic assay facilitating the examination of clonal heterogeneity in functional studies of MAA in melanoma tumor biology. Recent investigations from this laboratory have focused on characterizing human melanoma associated antigens (MAA) found either as secreted or cell surface associated glycoproteins in human melanoma cell lines. In these studies, monoclonal and polyclonal antiserums to melanoma cell components have been developed to specifically identify these MAAs immunochemically and provide a means to study the structural biochemistry of these determinants. At this time we have identified two antigens on which our research efforts are targeted: 1) a 100,000 dalton secreted glycoprotein (100K) common to melanoma, sarcoma and neuroblastoma tumor cell lines, and 2) a 250,000 dalton-high molecular weight component glycoprotein-proteoglycan complex which is thus far restricted to melanoma cells. The ultimate goal of our efforts is two-fold. Initially, we hope to develop schemes to isolate these melanoma associated antigens in sufficient quantities to obtain detailed structural information on these molecules, and secondly, we wish to implicate these glycoproteins in functional aspects of the biology of metastatic human melanoma in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)