Characterization of infiltrating macrophages in high glucose-induced peritoneal fibrosis in rats

Abstract

Abstract. Alternatively activated macrophages (M2 macrophages) are involved in tissue remodeling and fibrosis, but their effects on peritoneal fibrosis (PF) induced by high glucose peritoneal dialysate have yet to be fully established. In this study, PF was induced in male Sprague-Dawley rats by intraperitoneal injection with Lactate-G4.25% dialysate (20 ml/rat/day) for 4 weeks. Control rats were given an intraperitoneal injection with saline. Establishment of the PF model was verified by Masson's trichrome and H&E staining. M1 macrophages (co-localization of CD68 and CCr7) and M2 macrophages (co-localization of CD68 and CD206) was assayed by immunofluorescence and immunohistochemistry. The levels of dialysate cytokines driving macrophage differentiation (including IFN-γ, IL-2 and IL-4) were detected by ELISA. The expression of transforming growth factor (TGF)-β, p-Smad3, p-Smad2/3 and Smad7 in M2 macrophages (co-localization of CD68, CD206 and TGF-β, or p-Smad3, or p-Smad2/3, or Smad7) was measured by immunofluorescence. We found that PF rats had significantly thicker peritoneal membranes compared to control rats, indicating the successful establishment of our PF model. Compared to controls, PF rats had more peritoneal macrophages (CD68 + cells), more peritoneal M1 macrophages and a greater percentage of peritoneal M2 macrophages. PF rats also had significantly greater levels of dialysate cytokine IL-4, which promotes differentiation to M2 macrophages, higher expression levels of TGF-β in peritoneal M2 macrophages, upregulation of phosphorylated Smad3 and Smad2/3, and downregulation of Smad7 in peritoneal M2 macrophages. Our results indicate that M2 macrophages may play an important role in PF induced by high glucose, and that the cytokine environment in the abdominal cavities of PF rats promotes differentiation to M2 macrophages. The function of M2 macrophages in PF may be related to the TGF-β/Smad signaling pathways.

RETRACTED ARTICLE: TREM-1 associated macrophage polarization plays a significant role in inducing insulin resistance in obese population

“…The M1 phenotype macrophages are induced by interferon (IFN)-γ and lipopolysaccharide (LPS). This leads to increased inducible nitric oxide synthase (iNOS), upregulation of macrophage MHC class II and CC (CC motif) chemokine receptor 7 (CCR7) expression [9]. IFN-γ, along with polarization of M1 macrophages, also promotes M1 cell expression of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-6, IL1β, IL12, and monocyte chemoattractant protein-1 (MCP-1) [10], leading to insulin resistance [11].…”

“…These M2 macrophages are predominantly activated by Th2 cytokines, mainly interleukin (IL)-4 and IL-13 [9]. In non-obese subjects, adipocytes release higher levels of adiponectin that improves insulin sensitivity and enhances M2 macrophage polarization [15].…”

Expression of area-specific M2-macrophage phenotype by recruited rat monocytes in duct-ligation pancreatitis

“…The absence of CD163 + cells among the donor GFP + cells confirmed that the recruited monocyte lineage did upregulate CD163 after infiltration into the interlobular area. CD206 (Calderon et al 2015 ; Hu et al 2012 ; Lawrence and Natoli 2011 ), CD163 (Cote et al 2013 ; Komohara et al 2006 ; Polfliet et al 2006 ), and arginase 1 (Lawrence and Natoli 2011 ) are all M2 macrophage markers, indicating that the recruited monocytes polarized to the M2 phenotype in that location.…”

“…As for IL-4-producing cells, innate cells such as eosinophils and mast cells are reported to produce this cytokine (Loke et al 2007 ). These cells are abundant in the peritoneal cavity, and inflammation of the peritoneal organs including the pancreas may well stimulate IL-4 secretion by these cells (Hu et al 2012 ). This cytokine might have penetrated the serosa covering the pancreas and polarized macrophages in the interlobular area to M2 phenotype in the present study.…”

“…Alexa Fluor ® 488 (Alexa-488)-labeled rabbit anti-GFP IgG was purchased from MBL (Woburn, MA), and rabbit anti-type IV collagen antibody and mice mAb to type IV collagen-like molecules (B12) were kind gifts of Dr. Y. Sado and Dr. T. Ezaki, respectively. CD206 (macrophage mannose receptor) and arginase 1 are reported to be markers of M2 macrophages (Calderon et al 2015 ; Hu et al 2012 ; Lawrence and Natoli 2011 ), whereas nitric oxide synthase-2 (NOS2) is an M1 macrophage marker (Lawrence and Natoli 2011 ). To detect these, we employed rabbit or goat polyclonal antibodies to human CD206, arginase 1, and NOS2 (Santa Cruz Biotechnology, Dallas, TX).…”