Annexin 1 Negatively Regulates IL-6 Expression via Effects on p38 MAPK and MAPK Phosphatase-1

Abstract

Annexin 1 (Anx-1) is a mediator of the anti-inflammatory actions of glucocorticoids, but the mechanism of its anti-inflammatory effects is not known. We investigated the role of Anx-1 in the regulation of the proinflammatory cytokine, IL-6. Lung fibroblast cell lines derived from Anx-1−/− and wild-type (WT) mice were treated with dexamethasone and/or IL-1. IL-6 mRNA and protein were measured using real-time PCR and ELISA, and MAPK pathway activation was studied. Compared with WT cells, unstimulated Anx-1−/− cells exhibited dramatically increased basal IL-6 mRNA and protein expression. In concert with this result, Anx-1 deficiency was associated with increased basal phosphorylated p38, JNK, and ERK1/2 MAPKs. IL-1-inducible phosphorylated p38 was also increased in Anx-1−/− cells. The increase in IL-6 release in Anx-1−/− cells was inhibited by inhibition of p38 MAPK. Anx-1−/− cells were less sensitive to dexamethasone inhibition of IL-6 mRNA expression than WT cells, although inhibition by dexamethasone of IL-6 protein was similar. MAPK phosphatase-1 (MKP-1), a glucocorticoid-induced negative regulator of MAPK activation, was up-regulated by dexamethasone in WT cells, but this effect of dexamethasone was significantly impaired in Anx-1−/− cells. Treatment of Anx-1−/− cells with Anx-1 N-terminal peptide restored MKP-1 expression and inhibited p38 MAPK activity. These data demonstrate that Anx-1 is an endogenous inhibitory regulator of MAPK activation and IL-6 expression, and that Anx-1 is required for glucocorticoid up-regulation of MKP-1. Therapeutic manipulation of Anx-1 could provide glucocorticoid-mimicking effects in inflammatory disease.

The regulation of TNFα production after heat and endotoxin stimulation is dependent on Annexin-A1 and HSP70

“…ANXA1 has also been shown to regulate MAPK and thus controls inflammation by playing a negative role in the regulation of the MAPK (Alldridge et al 1999;Yang et al 2006). In the present study, indeed, absence of ANXA1 induces a sustained activation of ERK after heat + LPS stimulation, which may be important for the protection against the heat stress response.…”

Anti-inflammatory functions of glucocorticoid-induced genes

“…It is expressed in response to GCs A Clark Anti-inflammatory functions of glucocorticoid-induced genes Page 18 of 53 in a wide variety of cell types including mast cells (Kassel et al, 2001), monocytes or macrophages (Abraham et al, 2006;Aeberli et al, 2006;Bhattacharyya et al, 2007;Chen et al, 2002;Zhao et al, 2005), microglia (Zhou et al, 2007), T lymphocytes , dermal, lung and synovial fibroblasts (Phillips et al, 2006;Toh et al, 2004;Yang et al, 2006), endothelial cells (Furst et al, 2007), osteoblasts (Engelbrecht et al, 2003;Leclerc et al, 2004), keratinocytes (Onda et al, 2006;Stojadinovic et al, 2006), adipocytes (Bazuine et al, 2004), lung epithelial cells (Chivers et al, 2006;Hermoso et al, 2004), airway smooth muscle cells (Issa et al, 2007) and HeLa cells (Imasato et al, 2002;Lasa et al, 2002). Typically expression is quite rapid (within one hour), sustained (up to 24 hours), requires relatively low concentrations of GC, and is blocked by the GR antagonist RU486.…”

“…Inflammatory responses of an AnxA1 null mouse strain were exaggerated (Chatterjee et al, 2005;Hannon et al, 2003;Warne et al, 2006;Yang et al, 2004), and cells derived from these mice overexpressed COX-2, IL-1β and -6 in response to pro-inflammatory stimuli (Croxtall et al, 2003;Damazo et al, 2006;Hannon et al, 2003;Yang et al, 2006;Yona et al, 2004;Yona et al, 2005), suggesting that AnxA1 is an endogenous inhibitor of inflammatory responses . It should be noted here that cells lacking AnxA1 also showed differences of morphology (Croxtall et al, 2003) and phagocytic properties , which might be indicative of altered membrane physiology.…”

“…Importantly, suppressive effects of GCs on carageenininduced oedema, zymosan-induced peritonitis and antigen-induced arthritis were imparied in AnxA1 -/-mice (Hannon et al, 2003;Yang et al, 2004). GCs failed to inhibit the expression of IL-6 and COX-2 in lung fibroblasts lacking AnxA1 (Hannon et al, 2003;Yang et al, 2006). In part this may be explained by the failure of AnxA1 -/-cells to express DUSP1 and inhibit p38 MAPK signalling (Yang et al, 2006).…”

“…GCs failed to inhibit the expression of IL-6 and COX-2 in lung fibroblasts lacking AnxA1 (Hannon et al, 2003;Yang et al, 2006). In part this may be explained by the failure of AnxA1 -/-cells to express DUSP1 and inhibit p38 MAPK signalling (Yang et al, 2006).…”