Morin Hydrate Inhibits TREM-1/TLR4-Mediated Inflammatory Response in Macrophages and Protects Against Carbon Tetrachloride-Induced Acute Liver Injury in Mice

Abstract

This study aims to investigate the protective effects of morin hydrate (MH) against acute liver injury induced by carbon tetrachloride (CCl4) in mice and to elucidate the possible molecular mechanism of action. Mice were pretreated with MH (50 mg/kg body weight) or vehicle by oral gavage once daily for 5 days, followed by intraperitoneal injection of a single dose of CCl4 (1 ml/kg in olive oil). Mice were sacrificed 24 h later; the blood and liver samples were harvested for analysis. We also used the model of lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages in vitro and examined the effects of MH and its mechanism of action on the inflammatory response. Our results revealed that MH remarkably attenuated liver histopathological alterations, serum transaminases, hepatocytes death, and inflammatory response induced by CCl4. Importantly, MH reduced expression of the triggering receptor expressed on myeloid cells-1 (TREM-1) and toll-like receptor 4 (TLR4) both in vivo and in vitro experiments. This inhibitory effect MH on expression of the TREM-1 and TLR4 in cell culture was further heightened after TREM-1 knockdown with small interfering RNA (siRNA). Moreover, MH dramatically suppressed the inhibitor of kappa B α (IκBα) degradation and subsequent nuclear factor-kappa B (NF-κB) p65 translocation into the nucleus and NF-κB-mediated cytokines, such as tumor necrosis factor α (TNF-α), interleukin (IL)-1β, and IL-6. Additionally, MH also ameliorated CCl4-induced oxidative stress by enhancing the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression in the injured livers. Taken together, MH has hepatoprotective activity, and this effect may be elicited by attenuating macrophage-mediated inflammatory responses via inhibition TREM-1/TLR4/NF-κB signaling and by regulating hepatic oxidative stress via enhancement Nrf2/HO-1 antioxidant pathway.

Myricetin Modulates Macrophage Polarization and Mitigates Liver Inflammation and Fibrosis in a Murine Model of Nonalcoholic Steatohepatitis

“…However, myricetin treatment abrogated the increase levels of TREM-1 gene and protein expression (Figures 7A-D). Activation of TREM-1 has been shown to trigger and aggravate inflammation, especially through synergism with TLRs signaling (13)(14)(15)(16); therefore, we further assessed the effects of myricetin on the mRNA expression of TLR2, TLR4, and its adapter protein MyD88. As expected, our result confirmed that myricetin treatment significantly inhibited TLR2/4-MyD88 signaling expression in livers from NASH mice.…”

“…Sections were counterstained with 4 ′ ,6-diamidino-2phenylindole (DAPI) and hematoxylin solution and observed with Nikon Eclipse Ti inverted microscope (Nikon, Amstelveen, The Netherlands). The TUNEL-positive nuclei (blue) were quantified under ×200 magnification in 5 randomly nonoverlapping fields and 5 animals of each group were assessed (16). The results were presented as the mean number of TUNEL + cells each field.…”

“…The dissected liver tissues from mice were fixed in 4% paraformaldehyde, washed with PBS (pH 7.4), embedded in optimum cutting temperature tissue compound (OCT compound, Sakura, Japan), and stored at −80 for 24 h (16). Then the sections (8µm in thickness) were prepared with a cryotome Cryostat (Leica, CM 1900, Germany).…”

“…The triggering receptor expressed on myeloid cells (TREM)-1 is a kind of immunoglobulin superfamily activation receptors express on neutrophils and monocyte macrophages (13,14). Upon activation, TREM-1 can trigger and augment inflammatory reaction, especially through synergism with toll-like receptors (TLRs) signaling in macrophages (13)(14)(15)(16). Moreover, several studies have already revealed that TREM-1 play an important role in regulating the activation of Kupffer cell and is associated with macrophages polarization, which amplifies acute and chronic inflammatory responses in diseases (17)(18)(19).…”

IL-1Ra Protects Hepatocytes from CCl4-Induced Hepatocellular Apoptosis via Activating the ERK1/2 Pathway

“…In liver injury, an increase in the expression of IL-1β, IL-6, or TNF-α was always associated with apoptosis of hepatocytes, and these cytokines were mainly derived from nonparenchymal cells in recent studies. 24,25 Interestingly, CCl 4 could directly stimulate hepatocytes to express these cytokines (►Fig. 4).…”