Adiponectin normalizes LPS-stimulated TNF-α production by rat Kupffer cells after chronic ethanol feeding

Abstract

Chronic ethanol feeding sensitizes Kupffer cells to activation by lipopolysaccharide (LPS), leading to increased production of tumor necrosis factor-α (TNF-α). Adiponectin treatment protects mice from ethanol-induced liver injury. Because adiponectin has anti-inflammatory effects on macrophages, we hypothesized that adiponectin would normalize chronic ethanol-induced sensitization of Kupffer cells to LPS-mediated signals. Serum adiponectin concentrations were decreased by 45% in rats fed an ethanol-containing diet for 4 wk compared with pair-fed rats. Adiponectin dose dependently inhibited LPS-stimulated accumulation of TNF-α mRNA and peptide in Kupffer cells from both pair- and ethanol-fed rats. Kupffer cells from ethanol-fed rats were more sensitive to both globular (gAcrp) and full-length adiponectin (flAcrp) than Kupffer cells from pair-fed controls with suppression at 10 ng/ml adiponectin after chronic ethanol feeding. Kupffer cells expressed both adiponectin receptors 1 and 2; chronic ethanol feeding did not change the expression of adiponectin receptor mRNA or protein. gAcrp suppressed LPS-stimulated ERK1/2 and p38 phosphorylation as well as IκB degradation at 100–1,000 ng/ml in Kupffer cells from both pair- and ethanol-fed rats. However, only LPS-stimulated ERK1/2 phosphorylation was sensitive to 10 ng/ml gAcrp. gAcrp also normalized LPS-stimulated DNA binding activity of early growth response-1 with greater sensitivity in Kupffer cells from rats fed chronic ethanol. In conclusion, these results demonstrate that Kupffer cells from ethanol-fed rats are more sensitive to the anti-inflammatory effects of both gAcrp and flAcrp. Suppression of LPS-stimulated ERK1/2 signaling by low concentrations of gAcrp was associated with normalization of TNF-α production by Kupffer cells after chronic ethanol exposure.

Molecular Mechanism for Adiponectin-dependent M2 Macrophage Polarization

“…This effect of flAcrp was more potent in Kupffer cells from ethanol-fed rats compared with pair-fed controls (Fig. 3B), consistent with previous data indicating that, after ethanol feeding, Kupffer cells are more sensitive to the anti-inflammatory effects of adiponectin compared with cells from pair-fed controls (25). In contrast, gAcrp had minimal effects on the expression of M2 markers (Fig.…”

“…1). This concentration of flAcrp (45 nM or 10 g/ml) maximally suppresses LPS-stimulated TNF-␣ mRNA expression in Kupffer cells (25). However, this response was not attenuated by siRNA knockdown of IL-10 expression, compared with Kupffer cells that were not transfected or transfected with scrambled siRNA (Fig.…”

“…Chronic Ethanol Feeding and Kupffer Cell Isolation-All procedures involving animals were approved by the Institutional Animal Care and Use Committee at the Cleveland Clinic. Chronic ethanol feeding to rats, as well as the isolation and culture of Kupffer cells, were performed as described previously (25). Briefly, rats were allowed free access to the Lieber-Decarli high fat complete liquid diet for 2 days and then randomly assigned to pair-fed or ethanol-fed groups.…”

“…Control rats were pair-fed a liquid diet in which maltose dextrins were substituted isocalorically for ethanol over the entire feeding period. Kupffer cells were isolated and cultured, as described previously (25). For experiments measuring IL-4 protein, Kupffer cells were isolated from chow-fed control rats.…”

Identification of a Cytochrome P4502E1/Bid/C1q-dependent Axis Mediating Inflammation in Adipose Tissue after Chronic Ethanol Feeding to Mice

“…Both insulin-stimulated glucose transport and the ability of insulin to inhibit lipolysis are reduced after chronic ethanol feeding (3) associated with the development of systemic insulin resistance and the development of hepatic steatosis (5). Chronic ethanol feeding also decreases circulating adiponectin (6,7), leptin, and resistin (8) in animal models.…”