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Stimulation of rat hepatocyte fibronectin production by monocyte-conditioned medium is due to interleukin 6
1Department of Surgery, Beth Israel Hospital, Boston, Massachusetts 02215.
Abstract:
In this report, conditioned media from LPS-stimulated monocytes increased rat hepatocyte production of fibronectin (Fn) in a dose-dependent manner. Preincubation of the conditioned media with anti-IL-6, but not with anti-IL-1 alpha, anti-IL-1 beta, or anti-TNF, completely neutralized the Fn-stimulating activity. 10-100 pg/ml of rIL-6 was sufficient to increase Fn production. Neither IL-1 nor TNF had an effect on Fn production. The Fn-stimulating activity of IL-6 could be specifically neutralized only with anti-IL-6, but not with anti-IL-1 or anti-TNF. The increased Fn produced was shown to be of the plasma rather than the cellular form. These results demonstrate that IL-6 is the factor in monocyte-conditioned media that stimulates Fn production, and that IL-6 is the monokine tested with such activity.
Insights
Interleukin-6 (IL-6) from stimulated monocytes drives fibronectin (Fn) production in rat hepatocytes. This study identifies IL-6 as the key monokine responsible for increased plasma fibronectin.
Area of Science:
- Immunology
- Hepatology
- Molecular Biology
Background:
- Monocyte-derived factors can influence liver function.
- Fibronectin (Fn) production is a key aspect of liver health and disease.
- Understanding monokine signaling in hepatocytes is crucial for liver research.
Purpose of the Study:
- To identify the specific monokine responsible for increased fibronectin production in rat hepatocytes.
- To investigate the role of Interleukin-6 (IL-6) in mediating this effect.
- To differentiate between plasma and cellular fibronectin production.
Main Methods:
- Culturing rat hepatocytes and stimulating monocytes with lipopolysaccharide (LPS).
- Assessing fibronectin production in hepatocytes exposed to conditioned media from stimulated monocytes.
- Utilizing neutralizing antibodies against various cytokines (IL-6, IL-1α, IL-1β, TNF) to identify the active factor.
- Quantifying fibronectin production and determining its source (plasma vs. cellular).
Main Results:
- Conditioned media from LPS-stimulated monocytes dose-dependently increased hepatocyte fibronectin production.
- Anti-IL-6 antibodies completely neutralized this fibronectin-stimulating activity.
- Recombinant IL-6 (10-100 pg/ml) was sufficient to increase fibronectin production.
- IL-1 and TNF did not affect fibronectin production, and IL-6 activity was specifically neutralized by anti-IL-6.
- The increased fibronectin was identified as the plasma form.
Conclusions:
- Interleukin-6 (IL-6) is the primary monokine in conditioned media responsible for stimulating fibronectin production in rat hepatocytes.
- IL-6, not IL-1 or TNF, mediates this effect.
- The study highlights IL-6's role in regulating plasma fibronectin synthesis by hepatocytes.