We previously reported that 17,8-estradiol inhibits cytokinestimulated bioassayable IL-6 and the steady-state level of IL-6 mRNA. To determine the molecular basis of this effect, the transient expression of chloramphenicol acetyltransferase (CAT) reporter plasmid driven by the human IL-6 promoter was studied here in HeLa or murine bone marrow stromal cells (MBA 13.2). 1713-estradiol (10-8 M) completely suppressed stimulated CAT expression in HeLa cells cotransfected with IL-6/CAT constructs and a human estrogen receptor (hER) expression plasmid; but had no effect on reporter expression in HeLa cells not transfected with hER. 17fl-estradiol also inhibited stimulated expression in MBA 13.2 cells (which express the estrogen receptor constitutively) without the requirement of cotransfection of the hER plasmid. The hormonal effects were indistinguishable between constructs containing a 1.2-kb fragment of the 5' flanking region of the IL-6 gene or only the proximal 225-bp fragment. However, yeast-derived recombinant hER did not bind to the 225-bp segment in DNA band shift assays, nor did the 225-bp fragment compete for binding of an estrogen response element oligonucleotide to yeast-derived estrogen receptor. These data suggest that 17,6-estradiol inhibits the stimulated expression of the human IL-6 gene through an estrogen receptor mediated indirect effect on the transcriptional activity of the proximal 225-bp sequence of the promoter. (J. Clin. Invest. 1994. 93:944-950.)

Pneumocystis carinji is an extracellular organism which is thought to require attachment to alveolar epithelial cells for its growth and replication in humans. Fibronectin (Fn) binding to P. carinji is essential for optimal P. carinfi attachment. This study demonstrates that gp120, a 110-120-kD membrane glycoprotein on P. carinji, mediates attachment of the organism to cultured lung cells and is the site of Fn binding to P. carinji. A "Cr-labeled P. carinfi binding assay was used to quantify attachment of the organism to the alveolar epithelial cell line A549. Addition of free gpl20, purified from whole P. carinji organisms, caused a significant decrease in attachment of P. carinti to A549 cells from 44.2±5.5% to 22.4±4.2% (P < 0.01). Preincubation of the P. carinii organisms with a polyclonal antibody to gpl20 also resulted in a marked decrease in P. carinji attachment to A549 cells from 46.8%±5.2% to 213±4.8% (P < 0.01). Furthermore, addition of free gp120 to P. carinfi organisms caused a significant reduction in specific binding of 125I-Fn to P. carinli (from 83.3±8.5 ng to 47.1±5.9 ng, P < 0.01). Similarly, anti-gpl20 antibody decreased specific Fn binding to P. carinfi from 74.3±8.4 ng to 25.5±5.3 ng (P < 0.001). Solubilized P. carriim organisms separated by gel electrophoresis and blotted with "'I-Fn demonstrated specific binding of the '2'I-Fn to gpl20. In addition, a specific anti-#,-integrin antiserum reacted with gpl20 by Western blot, suggesting structural homology between gpl20 and the t-subunit of integrins. Thus, the data suggest that the P. carinii membrane glycoprotein gpl20 functions as a Fn binding protein and is required for optimal P. carinji attachment to alveolar epithelial cells. (J. Clin. Invest. 1991. 88:403-407.)

Attachment of pathogens to host cells is a prerequisite for the development of many infections. Pneumocystis cainfif (PC) pneumonia is characterized by attachment of PC trophozoites to the alveolar epithelium. The mechanism of this process is unknown. Fibronectin (Fn) is a glycoprotein present in the alveolar space known to mediate cell-cell attachment, including the attachment of certain pathogens to host epithelial cells. In this study the binding of Fn to PC trophozoites has been characterized in vitro using '25I-Fn. Fn binds saturably and specifically to 6.4 X 105 binding sites per organism with an apparent binding constant, Kd, of 1.2 X 10-8 M. Fn binding to PC was inhibited by the addition of Arg-Gly-Asp-Ser (RGDS), a tetrapeptide containing the active site of the cell-binding domain of Fn. PC attachment to an alveolar epithelial cell line was quantified using 51Cr-labeled PC trophozoites. Attachment was decreased from 24±1.9% to 12.1±1% (P < 0.01) by the addition of an anti-Fn antibody, an effect that could be overcome by the addition of excess free Fn. It is concluded that binding of Fn to PC may be an important initial step in the attachment of the organism to alveolar epithelial cells. Furthermore, it appears that PC recognizes and binds to the RGDS cell attachment site of Fn. (J. Clin. Invest. 1990.

The effect of decreased renal function on the disposition and elimination of the nontricyclic antidepressant fluoxetine was examined in 25 adult male subjects after a single 40-mg oral dose. Blood samples for the measurement of fluoxetine and its active metabolite norfluoxetine were drawn 13 times in the first 48 hr after dosing and thrice weekly thereafter for 4 wk. All urine was collected in daily aliquots for 4 wk and was assayed for fluoxetine and norfluoxetine concentrations. The extent of fluoxetine binding to plasma protein was determined by equilibrium dialysis. Kinetic analyses were by noncompartmental methods. The drug and its metabolite were distributed over a large apparent volume and both were eliminated slowly. No correlations between the degree of renal dysfunction and the rate of elimination, volume of distribution, or protein binding were found. Plasma concentrations of fluoxetine and norfluoxetine were not significantly changed by hemodialysis.

Pneumocystis carinji (PC) pneumonia begins as an intra-alveolar process resulting in injury to the alveolar epithelium with subsequent invasion of the lung interstitium. The clearance of PC organisms from the alveolar space is a critical function of alveolar macrophages (AM), the resident alveolar phagocytic cells. In this study the mechanism of PC attachment' to AM was determined using 51Cr-labeled organisms, with PC attachment reaching a maximum of 18.9±2.5% after 4 h. Attachment was significantly decreased'by preincubation of the AM with' a monoclonal anti-fibronectin antibody directed againstthe cell attachment site of fibronectin (from 17.8±2.2% to 8.3±1.0%, P <'0.01), or by addition of the fibronectin cell binding site analogue Arg-Gly-Asp-Ser (RGDS) (from 18.1±2.3% to 2.9±0.8%, P < 0.01). An anti-fibronectin monoclonal antibody directed against the heparin binding domain of fibronectin had no effect on PC attachment. Addition of the specific calcium ion chelating agent EGTA to the culture media similarly decreased attachment from 16.9±2.0% to 5.1±1.1% (P < 0.01). Fibronectin-mediated attachment of PC to AM did not result'in phagocytosis of the organisms by the AM as determined by chemiluminescence measurements. Therefore, the data indicate that PC attachment to AM is a calcium-dependent process mediated by the cell binding domain of fibronectin which does not trigger a phagocytic response by the