Publications

Hepatic lipocytes (perisinusoidal, Ito cells) are the primary matrix-producing cells in liver fibrosis. During liver injury they undergo activation, a process characterized by cell proliferation and increased fibrogenesis. We and others have established a culture model in which in vivo features of lipocyte activation can be mimicked by cells grown on plastic. Additionally, we recently showed that activation is associated with new expression of smooth muscle-specific alpha-actin both in vivo and in culture. Although interferon-gamma is known to inhibit collagen production in some systems, its action as a general modulator of lipocyte activation has not been examined; this issue forms the basis for our study. In culture-activated lipocytes, interferon-gamma (1,000 U/ml) significantly inhibited lipocyte proliferation as assessed by [3H]thymidine incorporation assay and nuclear autoradiography. In time-course studies of activation, it also markedly reduced expression of smooth muscle-specific alpha-actin and its messenger RNA. In dose-response experiments, maximal inhibitory effects on smooth muscle-specific alpha-actin mRNA gene expression were achieved with as little as 10 U interferon-gamma/ml. Inhibition of cellular activation was reversible; after interferon-gamma withdrawal, messenger RNA levels of smooth muscle-specific alpha-actin returned to untreated control levels. The effect of interferon-gamma extended to extracellular matrix gene expression, with reduction of type I collagen, type IV collagen and total fibronectin messenger RNAs to 3%, 24% and 15% of untreated control levels, respectively. In contrast to the marked effects on smooth muscle-specific alpha-actin and extracellular matrix gene expression, interferon-gamma reduced total protein synthesis by only 17.7%.(ABSTRACT TRUNCATED AT 250 WORDS)

The suicide substrate 3,5-dicarbethoxy-2,6-dimethyl-4-ethyl-1,4- dihydropyridine (DDEP) inactivates rat liver cytochrome P450 (P450) 3A isozymes through prosthetic heme alkylation of the apoprotein in a mechanism-based fashion, which marks them for rapid proteolysis. In this article, through the use of epitope-specific monoclonal antibodies, we show that both 3A1 and 3A2 isozymes are targeted for proteolysis. Furthermore, using intact rats, isolated rat hepatocytes, and rat liver subcellular fractions supplemented with ATP and MgCl2, as well as various proteolytic inhibitors as probes, we now report that the hepatic cytosolic ubiquitin-dependent proteolytic system rather than hepatic lysosomes is involved in the rapid degradation of DDEP-induced heme alkylated P450s 3A.

Systemic lupus erythematosus (SLE) is associated with multiple cardiac complications, including valvular damage and an increased risk of bacterial endocarditis. The purpose of this study was to evaluate prospectively a group of patients with SLE for the presence of valvular abnormalities in order to assess their candidacy for antibiotic prophylaxis prior to invasive dental procedures. Of the 43 participants, 19 (44%) had echocardiographic evidence of valvular pathology; however, only seven (16%) had a physical exam consistent with pathologic valve anatomy or function. Because of the high percentage of SLE patients with valvular abnormalities, and the poor sensitivity of the physical exam, referral to a cardiologist for echocardiography is suggested prior to invasive dental care for patients with SLE. If cardiac valvular pathology is detected, antibiotic prophylaxis should be considered.

The integrin family is composed of a large number of heterodimers, each one mediating distinct interactions with extracellular matrix and/or cell surface ligands. The expression of integrins appears to be tightly regulated in vivo, but the mechanisms by which cells control the formation and surface expression of specific pairs of subunits have not been well characterized. Two integrin subunits, the alpha subunit alpha v, and the beta subunit beta 1, could pose special problems in regulation because of their capacity to associate with multiple partners. In the present study, we have examined the effects of the cytokine transforming growth factor beta 1 (TGF-beta 1) on the expression of alpha v- and beta 1-containing integrins in primary cultures of guinea pig airway epithelial cells, e.g. cells that we have previously found to express multiple potential partners for both alpha v and beta 1. TGF-beta 1 increased the surface expression of both alpha v- and beta 1-containing heterodimers after periods of stimulation from 24 to 72 h. These increases in surface expression were associated with significant increases in the concentrations of mRNA encoding each of the partners of alpha v and beta 1, but with only minimal increases in mRNA encoding alpha v and beta 1 themselves. Airway epithelial cells metabolically labeled with [35S]methionine during stimulation with TGF-beta 1 demonstrated only a minimal increase in the synthesis of new alpha v protein at a time when synthesis of alpha v's beta subunit partners and surface expression of alpha v-containing heterodimers were dramatically increased. These data suggest that, at least in some cells, promiscuous integrin subunits (both alpha and beta) may normally be synthesized in excess. Thus, the surface expression of specific integrin heterodimers can be regulated primarily through regulation of the synthesis of the specific partners of these subunits.