Adult human vascular endothelial cells express the IL6 gene differentially in response to LPS or IL1

Genes for interleukin-1, interleukin-6, and tumor necrosis factor are expressed at markedly reduced levels in the livers of patients with severe liver disease

The genes for interferon (IFN) alpha, IFN gamma, IL-1 beta, IL-6, and TNF alpha were transcribed at readily detectable levels both in liver biopsies from individuals with normal liver function and in samples of normal viable liver taken for transplantation. These results provided evidence for the concept that such multifunctional cytokines play a role in homeostasis in normal human tissues. In normal human liver, in situ hybridization studies showed that, in the absence of a detectable inflammatory response, both hepatocytes and mononuclear cells exhibited a similar degree of expression of IL-6 mRNA in keeping with the finding that IL-6 is produced by cells of different lineages. The levels of IL-1, IL-6, and TNF mRNA were found to be markedly reduced in extracts of the livers of patients with primary biliary cirrhosis and other forms of autoimmune liver disease at a time when extensive liver lesions were apparent, compared to the levels of expression of these cytokines in the livers of normal individuals. The reduced expression of IL-1, IL-6, and TNF mRNAs appeared to be a specific effect and not due to a general reduction in RNA synthesis as the IFN alpha, IFN gamma and actin mRNAs were expressed at similar levels in both normal and diseased livers. The levels of IL-1 beta, IL-6, and TNF mRNAs were also reduced in samples of liver from a patient with a drug induced fulminant hepatitis suggesting that this specific pattern of altered cytokine gene expression was characteristic of the advanced stage of severe liver disease.

Cytokine induction by lipopolysaccharide (LPS) corresponds to lethal toxicity and is inhibited by nontoxic Rhodobacter capsulatus LPS

Many pathological effects of gram-negative bacteria are produced by their cell wall-derived lipopolysaccharides (LPSs). Differing pathogenicity of gram-negative LPSs, however, may depend on their capacities to induce cytokines. Thus, we studied the lethal toxicity of four nonenterobacterial LPSs and compared it with their capacity to induce mononuclear cell (MNC)-derived interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor (TNF). Unstimulated MNC did not release these cytokines. LPS from the phototrophic strain Rhodobacter capsulatus 37b4 elaborated little toxicity in galactosamine-treated mice (10 micrograms of LPS per mouse was the 100% lethal dose [LD100]) and induced IL-1 and IL-6 release only at high concentrations (10 to 50 micrograms of LPS per ml). R. capsulatus LPS failed to induce TNF activity even at the highest concentration tested (100 micrograms of LPS per ml). In contrast, LPS derived from Pseudomonas diminuta NCTC 8545 or the nodulating species Bradyrhizobium lupini DSM 30140 and Rhizobium meliloti 10406 expressed lethal toxicity (LD100, 1,000, 100, and 10 ng per mouse, respectively) and induced IL-1 or IL-6 (10 to 100, 10, and 1 ng of LPS per ml, respectively) at concentrations 1,000- to 10,000-fold lower than effective levels of R. capsulatus LPS. LPSs from P. diminuta, B. lupini, and R. meliloti also stimulated TNF production and release. MNC accumulated cell-associated IL-1 activities under circumstances in which released activity was readily detected. The cells contained only scant IL-6 activity, indicating release of this mediator rather than intracellular accumulation. Antisera to the respective cytokines inactivated biological activities of the samples selectively. The R. capsulatus LPS inhibited cytokine induction by LPS from P. diminuta, B. lupini, and R. meliloti in coincubation experiments. These results show that the in vivo lethality of the LPSs tested correlates with the induction of monocyte-derived cytokines in vitro. The results of this study suggest that the different lethality of various LPSs from gram-negative bacteria may be due to the differential ability of these LPSs to induce cytokine production.

Proliferating or interleukin 1-activated human vascular smooth muscle cells secrete copious interleukin 6

The cells that make up blood vessel walls appear to participate actively in local immune and inflammatory responses, as well as in certain vascular diseases. We tested here whether smooth muscle cells (SMC) can produce the important inflammatory mediator IL6. Unstimulated SMC in vitro elaborated 5 X 10(3) pg recIL6/24h (i.e., biological activity equivalent to 5 X 10(3) pg recombinant IL6 (recIL6), as determined in B9-assay with a recIL6 standard). Several pathophysiologically relevant factors augmented IL6 release from SMC including 10 micrograms LPS/ml (10(4) pg recIL6), 10 ng tumor necrosis factor/ml (4 X 10(4) pg recIL6), and most notably 10 ng IL1/ml (greater than or equal to 3.2 X 10(5) pg recIL6). Production of IL6 activity corresponded to IL6 mRNA accumulation and de novo synthesis. SMC released newly synthesized IL6 rapidly, as little metabolically labeled material remained cell-associated. In supernatants of IL1-stimulated SMC, IL6 accounted for as much as 4% of the secreted proteins. In normal vessels SMC seldom divide, but SMC proliferation can occur in hypertension or during atherogenesis. We therefore tested the relationship between IL6 production and SMC proliferation in response to platelet-derived growth factor (PDGF) in vitro. Quiescent SMC released scant IL6 activity, whereas PDGF (1-100 ng/ml) produced concentration-dependent and coordinate enhancement of SMC proliferation and IL6 release (linear regression of growth vs. IL6 release yielded r greater than 0.9). IL6 itself neither stimulated nor inhibited SMC growth or IL6 production. Intact medial strips studied in short-term organoid culture produced large quantities of IL6, similar to the results obtained with cultured SMC. These findings illustrate a new function of vascular SMC by which these cells might participate in local immunoregulation and in the pathogenesis of various important vascular diseases as well as in inflammatory responses generally.