Biomedical subjects

Bruce W Robb

Publications and source records attributed to Bruce W Robb.

22 records · Page 2Linked to original sources

PubMed2002

Interleukin-10 activates the transcription factor C/EBP and the interleukin-6 gene promoter in human intestinal epithelial cells.

BACKGROUND: Interleukin (IL)-6 is produced by enterocytes in response to sepsis and after treatment with IL-1beta. The IL-6 promoter contains binding sites for multiple transcription factors, including nuclear factor-kappaB and C/EBP. The anti-inflammatory cytokine IL-10 downregulates nuclear factor-kappaB activity, but its effects on C/EBP activation and IL-6 production in the enterocyte are not known. METHODS: Caco-2 cells were treated with IL-1beta, IL-10, or a combination of the cytokines. C/EBP DNA binding activity was determined by electrophoretic mobility shift assay and IL-6 levels by enzyme-linked immunosorbent assay. IL-6 promoter activation was assessed by luciferase assay. RESULTS: IL-10 treatment of cultured Caco-2 cells resulted in increased C/EBP DNA binding activity. Supershift analysis revealed upregulated DNA binding activity of C/EBP-beta but not C/EBP-delta. To examine if the increased DNA binding reflected gene activation, cells were transfected with a wild-type IL-6 promoter luciferase construct or with a mutated C/EBP binding site. IL-10 potentiated IL-1 beta-induced IL-6 promoter activity. Replacing the wild-type promoter with the promoter containing a mutated C/EBP DNA binding sequence blocked the effect of IL-10. When cells were treated with 0.5 ng/mL of IL-1 beta for 24 hours, IL-6 production increased, and this response to IL-1 beta was potentiated several-fold by IL-10. CONCLUSIONS: IL-10 may activate the IL-6 gene in stimulated enterocytes by upregulating the expression and activity of C/EBP.

CCAAT-Enhancer-Binding Proteins↗

PubMed2002

Multiple transcription factors regulating the IL-6 gene are activated by cAMP in cultured Caco-2 cells.

Mucosal and enterocyte IL-6 production is increased during sepsis and endotoxemia. Recent studies suggest that cAMP potentiates IL-6 production in endotoxin- or IL-1beta-stimulated enterocytes, but the molecular mechanisms are not known. We examined the role of the transcription factors NF-kappaB, activator protein (AP)-1, CCAAT/enhancer binding protein (C/EBP), and cAMP response element-binding protein (CREB) in cAMP-induced IL-6 production in cultured Caco-2 cells, a human intestinal epithelial cell line. In addition, the role of the protein kinase A (PKA), protein kinase C (PKC), and mitogen-activated protein (MAP) kinase signaling pathways was examined. Treatment of the cells with IL-1beta increased IL-6 production and activated the IL-6 promoter in cells transfected with a luciferase reporter plasmid containing a wild-type IL-6 promoter. These effects of IL-1beta were significantly potentiated by cAMP. When the binding sites for the individual transcription factors in the IL-6 promoter were mutated, results indicated that all four transcription factors may be involved in the cAMP-induced activation of the IL-6 gene. Treatment of the Caco-2 cells with cAMP increased the DNA binding activity of CREB, C/EBP, and AP-1, but not NF-kappaB. By using specific blockers, evidence was found that both PKA and p38 MAP kinase (but not PKC or p42/44 MAP kinase) may be involved in the cAMP-induced potentiation of IL-6 production. The present results suggest that cAMP activates multiple transcription factors involved in the regulation of the IL-6 gene and that the activation of these transcription factors may at least in part explain why cAMP potentiates IL-6 production in stimulated enterocytes.

Blotting, Western↗

PubMed2002

Proteasome inhibitors induce heat shock response and increase IL-6 expression in human intestinal epithelial cells.

In previous studies, the heat shock response, induced by hyperthermia or sodium arsenite, increased interleukin (IL)-6 production in intestinal mucosa and cultured human enterocytes. A novel way to induce the heat shock response, documented in other cell types, is treatment with proteasome inhibitors. It is not known if proteasome inhibition induces heat shock in enterocytes or influences IL-6 production. Here we tested the hypothesis that treatment of cultured Caco-2 cells, a human intestinal epithelial cell line, with proteasome inhibitors induces the heat shock response and stimulates IL-6 production. Treatment of Caco-2 cells with one of the proteasome inhibitors MG-132 or lactacystin activated the transcription factor heat shock factors (HSF)-1 and -2 and upregulated cellular levels of the 72-kDa heat shock protein HSP-72. The same treatment resulted in increased gene and protein expression of IL-6, a response that was blocked by quercetin. Additional experiments revealed that the IL-6 gene promoter contains a HSF-responsive element and that the IL-6 gene may be regulated by the heat shock response. The present results suggest that proteasome inhibition induces heat shock response and IL-6 production in enterocytes and that IL-6 may be a heat shock-responsive gene, at least under certain circumstances. The observations are important considering the multiple biological roles of IL-6, both locally in the gut mucosa and systemically, and considering recent proposals in the literature to use proteasome inhibitors in the clinical setting to induce the heat shock response.

Acetylcysteine↗

PubMedDate not supplied

Home oxygen therapy: adjunct or risk factor?

The use of home oxygen therapy has become increasingly commonplace and is frequently prescribed by medical specialists. In this study, we have identified a generally unexpected risk of home oxygen therapy. We performed a retrospective review of 3673 consecutive patients treated at our adult burn center over a 10-year period from 1992 to 2001. We identified 27 patients with burns directly attributable to oxygen therapy and also noted an increased incidence of these injuries over the study period. The average age of the patients was 68.1 +/- 9.2 years (range, 40-82 years). Twenty-three were using oxygen at home, three in nursing homes, and one was an inpatient in an acute care facility. Twenty-five patients (93%) were receiving oxygen therapy for the diagnosis of chronic obstructive pulmonary disease. Twenty-four patients (89%) were smoking while using oxygen, two were lighting pilot lights, and one was lighting his wife's cigarette. Four patients (15%) sustained burns greater than 10% TBSA. Seventeen patients (63%) had only partial thickness burns. Thirteen patients (48%) required admission for treatment of their burn injuries. The average length of stay for those admitted was 4.4 days. The average hospital charge for admitted patients was US dollars 8055. There were four deaths (15%), all of which were correlated only with the extent of injury. Although intuitively obvious to most health care professionals, not all patients understand that oxygen therapy and cigarettes or open flame can result in a significant injury. Although some practitioners have advocated not prescribing home oxygen for those who continue to smoke, an alternative means of reducing the incidence of this preventable complication appears warranted. Prevention efforts should focus on the counseling of patients and their caregivers as well as educating primary care physicians, nurses, and home health providers as to the dangers of oxygen use.

Accident Prevention↗