Inhibitory effect of FSLLRY-NH2 on inflammatory responses induced by hydrogen peroxide in HepG2 cells

The antioxidant activity of polysaccharides from Armillaria gallica

The purpose of this study was to investigate the antioxidant activity of Armillaria gallica polysaccharides. It explored whether Armillaria gallica polysaccharides (AgP) could prevent HepG2 cells from H2O2-induced oxidative damage. The results demonstrated that HepG2 cells were significantly protected by AgP, and efficiently suppressed the production of reactive oxygen species (ROS) in HepG2 cells. Additionally, AgP significantly decreased the abnormal leakage of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) caused by H2O2, protecting cell membrane integrity. It was discovered that AgP was also found to regulate the activities of antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX), while reducing malondialdehyde (MDA), thus protecting cells from oxidative damage. According to the flow cytometry analysis and measurement of caspase-3, caspase-8, and caspase-9 activities, AgP could modulate apoptosis-related proteins and attenuate ROS-mediated cell apoptosis.

FSLLRY-NH2, a protease-activated receptor 2 (PAR2) antagonist, activates mas-related G protein-coupled receptor C11 (MrgprC11) to induce scratching behaviors in mice

AIMS

Protease-activated receptor 2 (PAR2), a type of G protein-coupled receptor (GPCR), plays a significant role in pathophysiological conditions such as inflammation. A synthetic peptide SLIGRL-NH₂ (SLIGRL) can activate PAR2, while FSLLRY-NH₂ (FSLLRY) is an antagonist. A previous study showed that SLIGRL activates both PAR2 and mas-related G protein-coupled receptor C11 (MrgprC11), a different type of GPCR expressed in sensory neurons. However, the impact of FSLLRY on MrgprC11 and its human ortholog MRGPRX1 was not verified. Hence, the present study aims to verify the effect of FSLLRY on MrgprC11 and MRGPRX1.

METHODS

The calcium imaging technique was applied to determine the effect of FSLLRY in HEK293T cells expressing MrgprC11/MRGPRX1 or dorsal root ganglia (DRG) neurons. Scratching behavior was also investigated in wild-type and PAR2 knockout mice after injecting FSLLRY.

KEY FINDINGS

It was surprisingly discovered that FSLLRY specifically activates MrgprC11 in a dose-dependent manner, but not other MRGPR subtypes. Furthermore, FSLLRY also moderately activated MRGPRX1. FSLLRY stimulates downstream pathways including Gα_q/11, phospholipase C, IP₃ receptor, and TRPC ion channels to evoke an increase in the intracellular calcium levels. The molecular docking analysis predicted that FSLLRY interacts with the orthosteric binding pocket of MrgprC11 and MRGPRX1. Finally, FSLLRY activated primary cultures of mouse sensory neurons, and induced scratching behaviors in mice.

SIGNIFICANCE

The present study has revealed that FSLLRY is capable of triggering itch sensation through activation of MrgprC11. This finding highlights the importance of considering the unexpected activation of MRGPRs in future therapeutic approaches aimed at the inhibition of PAR2.

Inhibition of Protease Activated Receptor 2 Attenuates HBx-Induced Inflammation and Mitochondria Oxidative Stress

BACKGROUND

Hepatitis B virus (HBV) infection is one of the global public problems. Among the known infection cases, HBV X protein (HBx) is one of the key inducements of viral replication and host infection. This study was aimed to uncover the role of protease activated receptor 2 (PAR2) on HBx-induced liver injury.

METHODS

A PAR2-KO mouse model expressing HBx was constructed using hydrodynamics-based in vivo gene transfection method. In addition, pcDNA3.1-HBx was used to over-express HBx in LO2 cells. The effects of HBx overexpression on inflammation and mitochondria oxidative stress were evaluated.

RESULTS

We found that PAR2 protein level was increased by HBx overexpression. The enforced HBx inhibited LO2 cells apoptosis. Meanwhile, HBx induced inflammation reactions through promoting the secretion of pro-inflammatory cytokines such as TNF-α, IL-6, and CXCL-2. Overexpressed HBx also resulted in mitochondria oxidative stress by upregulation of ROS level and downregulation of MMP and ATP. However, in FSLLRY-NH2 (PAR2 antagonist) treated LO2 cells or PAR2-KO mice, PAR2 blockade reversed the above adverse effects of HBx on liver cells or tissues.

CONCLUSION

Inhibition of PAR2 may suppress inflammation and mitochondria oxidative stress caused by HBx, pointing out the potential application values of PAR2 antagonist on the treatment of HBV infection in clinic.

The development of proteinase-activated receptor-2 modulators and the challenges involved

Protease-activated receptor-2 (PAR2) has been extensively studied since its discovery in the mid-1990. Despite the advances in understanding PAR2 pharmacology, it has taken almost 25 years for the first inhibitor to reach clinical trials, and so far, no PAR2 antagonist has been approved for human use. Research has employed classical approaches to develop a wide array of PAR2 agonists and antagonists, consisting of peptides, peptoids and antibodies to name a few, with a surge in patent applications over this period. Recent breakthroughs in PAR2 structure determination has provided a unique insight into proposed PAR2 ligand binding sites. Publication of the first crystal structures of PAR2 resolved in complex with two novel non-peptide small molecule antagonists (AZ8838 and AZ3451) revealed two distinct binding pockets, originally presumed to be allosteric sites, with a PAR2 antibody (Fab3949) used to block tethered ligand engagement with the peptide-binding domain of the receptor. Further studies have proposed orthosteric site occupancy for AZ8838 as a competitive antagonist. One company has taken the first PAR2 antibody (MEDI0618) into phase I clinical trial (NCT04198558). While this first-in-human trial is at the early stages of the assessment of safety, other research into the structural characterisation of PAR2 is still ongoing in an attempt to identify new ways to target receptor activity. This review will focus on the development of novel PAR2 modulators developed to date, with an emphasis placed upon the advances made in the pharmacological targeting of PAR2 activity as a strategy to limit chronic inflammatory disease.

Hepatoprotective effect of sodium hydrosulfide on hepatic encephalopathy in rats

Hydrogen sulfide is well-known to exhibit anti-inflammatory and cytoprotective activities, and also has protective effects in the liver. This study aimed to examine the protective effect of hydrogen sulfide in rats with hepatic encephalopathy, which was induced by mild bile duct ligation. In this rat model, bile ducts were mildly ligated for 26 days. Rats were treated for the final 5 days with sodium hydrosulfide (NaHS). NaHS (25 µmol/kg), 0.5% sodium carboxymethyl cellulose, or silymarin (100 mg/kg) was administered intraperitoneally once per day for 5 consecutive days. Mild bile duct ligation caused hepatotoxicity and inflammation in rats. Intraperitoneal NaHS administration reduced levels of aspartate aminotransferase and alanine aminotransferase, which are indicators of liver disease, compared to levels in the control mild bile duct ligation group. Levels of ammonia, a major causative factor of hepatic encephalopathy, were also significantly decreased. Malondialdehyde, myeloperoxidase, catalase, and tumor necrosis factor-α levels were measured to confirm antioxidative and anti-inflammatory effects. N-Methyl-D-aspartic acid (NMDA) receptors with neurotoxic activity were assessed for subunit NMDA receptor subtype 2B. Based on these data, NaHS is suggested to exhibit hepatoprotective effects and guard against neurotoxicity through antioxidant and anti-inflammatory actions.