Publications

Laminin, a glycoprotein with a molecular weight of approximately 850,000 daltons, is a major constituent of most epithelial basement membranes. Its presence in the extracellular matrix of normal liver, however, is debated. Using two affinity-purified antibodies directed against laminin, we have localized the glycoprotein within normal rat liver and identified its cellular source. Immunofluorescent staining of rat liver sections revealed laminin in a continuous distribution around hepatic sinusoids, adjacent to hepatocytes and sinusoidal lining cells. To determine the cellular origin of laminin, three perisinusoidal cell populations (hepatocytes, sinusoidal endothelial cells, and lipocytes) were purified from enzymatically dispersed rat liver and were established in primary culture. By immunofluorescence, laminin was associated almost exclusively with lipocytes. Synthesis of laminin was demonstrated by immunoprecipitation of the protein from lipocyte culture medium pulse-labeled with radioactive methionine. These results show that in adult liver, laminin is present in the perisinusoidal matrix and is produced by hepatic lipocytes. Lipocytes, which have the capacity to produce collagen as well as laminin, may be the principal source of extracellular matrix proteins in the perisinusoidal space, and may contribute to subendothelial fibrosis resulting from liver injury.

Intravenously administered endotoxin inhibits the polymorphonuclear leukocyte (PMN)-dependent airway edema produced in guinea pigs exposed to toluene diisocyanate (TDI). Tumor necrosis factor (TNF) is produced in vivo by peripheral blood monocytes and tissue macrophages stimulated with endotoxin and has been shown to activate PMN's and vascular endothelial cells. To determine whether the inhibition of airway edema is mediated by TNF, guinea pigs were treated with intravenous saline or 75,000 U/kg recombinant human TNF 1.5 h before exposure to air or 3 ppm TDI for 1 h. Animals were then injected intravenously with 50 mg/kg Evans blue dye as a marker of protein extravasation. Saline-treated animals exposed to TDI had a significant increase in tracheal Evans blue dye extravasation (85 +/- 6.5 micrograms dye/g trachea, mean +/- SE) compared with saline-treated animals exposed to air (31.3 +/- 2.5, P less than 0.001). The tracheal extravasation of Evans blue dye was significantly inhibited (P less than 0.05) in TDI-exposed animals treated with TNF (64.7 +/- 7.5). Neither heat-inactivated TNF (104.9 +/- 9.5) nor TNF neutralized with a monoclonal antibody against TNF (99.7 +/- 17.9) inhibited TDI-induced airway edema. In addition, treatment with 15,000 U/kg (99.9 +/- 21.3) or 150,000 U/kg (103.2 +/- 17.6) interleukin 1, a monokine also produced in response to endotoxin, did not prevent airway edema. These results suggest that TNF released in response to endotoxin mediates endotoxin's inhibition of a PMN-dependent airway edema.

Substance P and related tachykinins contribute to the airway hyperresponsiveness caused by toluene diisocyanate (TDI) in guinea pigs. Neutral endopeptidase (NEP) is an important modulator of substance P-induced responses. To test the hypothesis that exposure to TDI would increase responsiveness to substance P by inhibiting activity of this enzyme, we determined the dose of substance P required to increase pulmonary resistance by 200% above baseline (PD200) before and after administration of the pharmacologic inhibitor phosphoramidon in guinea pigs studied 1 h after a 1-h exposure to air or 3 ppm TDI. TDI exposure increased responsiveness to substance P significantly. However, phosphoramidon caused a significantly greater leftward shift of the substance P dose-response curve in air-exposed animals than it did in TDI-exposed animals, so that after phosphoramidon, mean values of PD200 in animals exposed to air or TDI did not differ. Tracheal NEP activity was significantly less after exposure to TDI than after exposure to air, whereas activity in the esophagus was the same in both groups. These results suggest that TDI exposure increases the bronchoconstrictor responsiveness of guinea pigs to substance P, in large part through inhibition of airway NEP.

Systemic lupus erythematosus (SLE) in humans and in mice is characterized by reduced suppressor T-cell activity. This observation suggests that selective loss or impaired function of suppressor T cells may contribute to the development of autoimmunity. To clarify the role of suppressor T cells in the pathogenesis of SLE, we used a rat MAb to selectively deplete Lyt-2+ ('suppressor/cytotoxic') T cells from lupus-prone NZB/NZW F1 (B/W) mice. Treatment consisted of weekly intraperitoneal injections of anti-Lyt-2 (2 mg/mouse) beginning at age 4 months, prior to the onset of overt clinical illness. Control mice received weekly injections of either non-immune rat IgG or saline. Despite sustained depletion of Lyt-2+ T cells, mice treated with anti-Lyt-2 were indistinguishable from control mice with respect to production of anti-DNA antibodies, development of renal disease, and mortality. These findings imply that Lyt-2+ T cells do not regulate autoimmunity in B/W mice. However, they do not exclude the possibility that Lyt-2+ T cells suppress autoimmunity in normal mice but are simply non-functional in B/W mice. Therefore, we also examined the consequences of depleting Lyt-2+ T cells from non-autoimmune C57BL/6 x NZW (B6/NZW) mice. Depletion of Lyt-2+ T cells from B6/NZW from age 4 to 10 months produced neither serologic nor clinical evidence of murine lupus. These observations suggest that suppressor T cell defects are not sufficient to cause murine lupus.

We measured monoamine metabolites and biopterin in the CSF of 37 patients with dementia of the Alzheimer type (DAT), with or without extrapyramidal signs, and in 14 age-matched healthy controls. Compared with concentrations in DAT and controls, the concentrations of homovanillic acid (HVA) and biopterin were significantly decreased in DAT with extrapyramidal signs (EDAT). CSF 3-methoxy-4-hydroxy-phenethyleneglycol and 5-hydroxyindoleacetic acid did not differ significantly among these groups. Age at onset of dementia was positively correlated with CSF HVA (r = 0.49, p less than 0.05). The two dementia groups did not differ significantly in the extent of ventricular dilation as measured by quantitative CT, but EDAT patients had lower Mini-Mental State Examination scores than did DAT patients. When patients were matched for age and dementia severity, CSF HVA and biopterin concentrations remained significantly lower in EDAT than in DAT patients. These results indicate that EDAT patients form a distinct subgroup of DAT with evidence of central monoamine dysfunction.