Inhibitory effect of TGF-β1 on NO production in peritoneal macrophages from collagen-induced arthritis rats involving the LPS-TLR4 pathway

Abstract

Transforming growth factor-β1 (TGF-β1) is critical in controlling inflammatory responses and the prevention of autoimmune diseases. Although the effect of TGF-β1 on macrophages from normal mice or rats has been established, little attention has been paid to its effect on disease conditions. In the present study, we investigated the regulatory effect, and possible mechanism, of TGF-β1 exposure on the secretion of nitric oxide (NO) in peritoneal macrophages (PMΦ) obtained from collagen-induced arthritis (CIA) rats. The CIA model was established by immunizing the emulsion of collagen type II and incomplete Freund's adjuvant (IFA) in Wistar rats. PMΦ were incubated with TGF-β1 (5 ng/ml) for 36 h and the supernatant, and cell mRNA and protein were collected. NO concentration was determined using an NO assay kit. The mRNA expression of inducible nitric oxide synthase (iNOS) and Toll-like receptor 4 (TLR4) was determined using reverse transcription-polymerase chain reaction (RT-PCR). The protein expression of iNOS was tested with western blot analysis. The expression of membrane TLR4 was determined by flow cytometry. We discovered that the secretion of NO from the PMΦ of CIA rats increased compared with normal rats. TGF-β1 significantly inhibited the production of NO in the PMΦ from CIA rats. iNOS mRNA and protein expression in the PMΦ from CIA rats may be suppressed by TGF-β1. TLR4 mRNA and protein expression in PMΦ from CIA rats were upregulated with LPS stimulation and treatment with TGF-β1 inhibited their expression. These results demonstrated that TGF-β1 inhibited lipopolysaccharide (LPS)-induced NO production in the PMΦ from CIA rats, which may be due to the inhibition of the LPS-TLR4 signaling pathway.

The Role of Membrane-embedded DUOX2 on Ectodomain Shedding via G protein-coupled Receptor Signaling

“…RNA interference of GRK2 also increased membrane-bound fractalkine levels as measured by ELISA (Figure 10a) and western blotting (Figure 10b). NOS2/iNOS mRNA and protein expression in macrophages was also reported to be inhibited by TGFβ1 [55]. This led us to hypothesize that TGFβ1 may regulate peroxynitrite generation and shedding of fractalkine.…”

“…SP/NK1R signaling activates Gα q , leading to Ca 2+ mobilization and activation of protein kinase C, and protein kinase C upregulates NOS2/iNOS induction of NO synthesis [36,55]. Gaq signaling recruits β arrestin 2 to NK1R, and β arrestin 2 activates PI3K-Akt [56], leading to the induction of NOS2/iNOS expression [57].…”

ER‐α36 is involved in calycosin inhibition of IL‐6 production in macrophages

“…The THP‐1 cell line has been widely used to study immune responses because the cells are not only in the monocyte state but also in the macrophage‐like state 36 . As a specific LPS transmembrane receptor, TLR4 interacts with LPS to activate the LPS signal transduction pathways that enhance NF‐κB activity 37 . Activated NF‐κB increases the transcription of several cytokines, such as TNF‐α and IL‐6 38 .…”

Effect of Melilotus extract on lung injury via the upregulation of tumor necrosis factor-α-induced protein-8-like 2 in septic mice

“…TLR4, a specific LPS transmembrane receptor, initiates the production of proinflammatory cytokines and corresponding immune response following LPS activation ( 37 ). LPS combines with LPS-binding protein (LBP) to form the LPS-LBP complex, which then binds with CD14 (mCD14) on the surface of the cell membrane to form a complex.…”