Pioglitazone-Mediated Attenuation of Experimental Colitis Relies on Cleaving of Annexin A1 Released by Macrophages

Abstract

Ulcerative colitis and Crohn’s disease are chronic inflammatory bowel diseases (IBDs) which burden health systems worldwide; available pharmacological therapies are limited and cost-intensive. Use of peroxisome proliferator activated-receptor γ (PPARγ) ligands for IBD treatment, while promising, lacks solid evidences to ensure its efficacy. Annexin A1 (AnxA1), a glucocorticoid-modulated anti-inflammatory protein, plays a key role on IBD control and is a potential biomarker of IBD progression. We here investigated whether effects of pioglitazone, a PPARγ ligand, rely on AnxA1 actions to modulate IBD inflammation. Experimental colitis was evoked by 2% dextran sodium sulfate (DSS) in AnxA1 knockout (AnxA1−/−) or wild type (WT) C57BL/6 mice. Clinical and histological parameters were more severe for AnxA−/− than WT mice, and 10 mg/kg pioglitazone treatment attenuated disease parameters in WT mice only. AnxA1 expression was increased in tissue sections of diseased WT mice, correlating positively with presence of CD68+ macrophages. Metalloproteinase-9 (MMP-9) and inactive 33 kDa AnxA1 levels were increased in the colon of diseased WT mice, which were reduced by pioglitazone treatment. Cytokine secretion, reactive oxygen species generation and MMP-9 expression caused by lipopolysaccharide (LPS) treatment in AnxA1-expressing RAW 264.7 macrophages were reduced by pioglitazone treatment, effects not detected in AnxA1 knockdown macrophages. LPS-mediated increase of AnxA1 cleaving in RAW 264.7 macrophages was also attenuated by pioglitazone treatment. Finally, pioglitazone treatment increased extracellular signal-regulated kinase (ERK) phosphorylation in AnxA1-expressing RAW 264.7 macrophages, but not in AnxA1-knockdown macrophages. Thus, our data highlight AnxA1 as a crucial factor for the therapeutic actions of pioglitazone on IBDs.

Effects of Formyl Peptide Receptor Agonists Ac9-12 and WKYMV in In Vivo and In Vitro Acute Inflammatory Experimental Models

“…The signal transduction pathways of mitogen-activated kinases (MAPKs) are highly evolutionarily conserved in eukaryotic cells and contribute to the regulation of several cellular responses, including activation of inflammatory cells, cytokine production, proliferation, differentiation, and cell death [ 48 ]. LPS activates the MAPK cascade by binding to TLR4 and, in macrophages, this activation results in the release of pro-inflammatory cytokines (IL-1β, IL-6, IL-10, and TNF-α), reactive oxygen species, and nitric oxide, all of which contribute to tissue inflammatory response [ 49 , 50 , 51 ]. Similarly, phosphorylation of MAPKs occurs after activation of Fprs by their ligands, triggering numerous cellular responses that can be pro or anti-inflammatory depending on the type of ligand [ 52 , 53 ].…”

Prophylactic Catechin-Rich Green Tea Extract Treatment Ameliorates Pathogenic Enterotoxic Escherichia coli-Induced Colitis

“…Anex1 is a glucocorticoid-induced protein that inhibits phospholipase A2 activity, thereby suppressing eicosanoid synthesis and inflammatory processes [33]. Several studies focused on the anti-inflammatory effect of Anex1 in the treatment of various inflammatory bowel diseases and revealed its therapeutic potency through suppressed inflammatory signals [34,35]. Previously, Babbin et al [36] reported that aggravated intestinal damage in an Anex1 knockout mouse model was followed by suppressed ALX/FPRL-1 under dextran sulfate sodium-induced colitis conditions, which suggests the importance of Anex1 in modulating intestinal inflammation and mucosal injury.…”

The Molecular Mechanisms of Intestinal Inflammation and Fibrosis in Crohn’s Disease

“…For instance, when mice with a targeted disruption of the PPARγ gene in the intestinal epithelial cells (generated using the villin-Cre transgene and floxed PPARγ allele) were treated with dextran sodium sulfate (DSS), the expressions of interleukin 6 (IL-6), IL-1β, and TGFα mRNAs were increased in their colons, as compared to the corresponding levels in the control mice (Adachi et al, 2006). Interestingly, in the DSS model mice, administration of pioglitazone or rosiglitazone, which are full agonists of PPARγ, can improve intestinal inflammation (Adachi et al, 2006;da Rocha et al, 2020). The novel 5-ASA analog, GED-0507-34 Levo (GED), is also able to activate PPARγ and suppress the expression of the primary protein markers of fibrosis, namely alpha-smooth muscle actin (α-SMA) and collagen I-II, by inhibiting the TGF-β/Smad pathway in the DSS mouse model as well as in human intestinal fibroblasts (Speca et al, 2016).…”