Protective role of casuarinin from Melastoma malabathricum against a mouse model of 5-fluorouracil-induced intestinal mucositis: Impact on inflammation and gut microbiota dysbiosis.

BACKGROUND: 5-FU-induced intestinal mucositis (FUIIM) is a common gastrointestinal side effect of chemotherapy, leading to gastric pain in clinical cancer patients. In a previous study, we demonstrated that neutrophil elastase (NE) inhibitors could alleviate FUIIM and manipulate the homeostasis of the gut microbiota. The root of Melastoma malabathricum, also called Ye-Mu-Dan, has been used as a traditional Chinese medicine for gastrointestinal disease. Water extract of the roots of M. malabathricum exhibits an inhibitory effect on NE, with an IC50 value of 9.13 µg/ml. PURPOSE: In this study, we aimed to isolate an anti-NE compound from the root of M. malabathricum and to determine the protective effect of the bioactive component on a mouse model of FUIIM with respect to tissue damage, inflammation, intestinal barrier dysfunction, and gut microbiota dysbiosis. METHODS: A water extract of the roots of M. malabathricum was prepared and its major bioactive compound, was identified using bioactivity-guided fractionation. The effects of samples on the inhibition of NE activity were evaluated using enzymatic assays. To evaluate the effects of the bioactive compound in an FUIIM animal model, male C57BL/6 mice treated with or without casuarinin (50 and 100 mg/kg/day, p.o.), and then received of 5-fluorouracil (50 mg/kg/day) intraperitoneally for 5 days to induce FUIIM. Histopathological staining was used to monitor the tissue damage, proliferation of intestinal crypts, and expression of tight junction proteins. The inflammation score was estimated by determining the levels of oxidative stress, neutrophil-related proteases, and proinflammatory cytokines in tissue and serum. The ecology of the gut microbiota was evaluated using 16S rRNA gene sequencing. RESULTS: Casuarinin had the most potent and selective effect against NE, with an IC50 value of 2.79 ± 0.07 µM. Casuarinin (100 mg/kg/day, p.o.) significantly improved 5-FU-induced body weight loss together with food intake reduction, and it also significantly reversed villus atrophy, restored the proliferative activity of the intestinal crypts, and suppressed inflammation and intestinal barrier dysfunction in the mouse model of FUIIM. Casuarinin also reversed 5-FU-induced gut microbiota dysbiosis, particularly the abundance of Actinobacteria, Candidatus Arthromitus, and Lactobacillus murinus, and the Firmicutes-to-Bacteroidetes ratio. CONCLUSION: This study firstly showed that casuarinin isolated from the root part of M. malabathricum could be used as a NE inhibitor, whereas it could improve FUIIM by modulating inflammation, intestinal barrier dysfunction, and gut microbiota dysbiosis. In summary, exploring anti-NE natural product may provide a way to find candidate for improvement of FUIIM.

Honokiol suppresses TNF-α-induced neutrophil adhesion on cerebral endothelial cells by disrupting polyubiquitination and degradation of IκBα.

Adhesion molecules expressed on cerebral endothelial cells (ECs) mediate leukocyte recruitment and play a significant role in cerebral inflammation. Increased levels of adhesion molecules on the EC surface induce leukocyte infiltration into inflammatory areas and are thus hallmarkers of inflammation. Honokiol, isolated from the Chinese medicinal herb Magnolia officinalis, has various pharmacological activities, including anti-inflammatory effects, yet the nature of honokiol targeting molecules remains to be revealed. Here, we investigated the inhibitory effect of honokiol on neutrophil adhesion and vascular cell adhesion molecule-1 (VCAM-1) expression, which underlie its molecular target, and mechanisms for inactivating nuclear factor κ enhancer binding protein (NF-κB) in mouse cerebral ECs. Honokiol inhibited tumour necrosis factor-α (TNF-α)-induced neutrophil adhesion and VCAM-1 gene expression in cerebral ECs. The inflammatory transcription factor NF-κB was downregulated by honokiol. Honokiol significantly blocked TNF-α-induced NF-κB p65 nuclear translocation and degradation of the proteasome-dependent inhibitor of NF-κB α (IκBα). From docking model prediction, honokiol directly targeted the ubiquitin-ubiquitin interface of Lys48-linked polychains. Moreover, honokiol prevented the TNF-α-induced Lys48-linked polyubiquitination, including IκBα-polyubiquitin interaction. Honokiol has protective anti-inflammatory effects on TNF-α-induced neutrophil adhesion and VCAM-1 gene expression in cerebral ECs, at least in part by directly inhibiting ubiquitination-mediated IκBα degradation and then preventing NF-κB nuclear translocation.

Anti-inflammatory effects of Perilla frutescens in activated human neutrophils through two independent pathways: Src family kinases and Calcium.

The leaves of Perilla frutescens (L.) Britt. have been traditionally used as an herbal medicine in East Asian countries to treat a variety diseases. In this present study, we investigated the inhibitory effects of P. frutescens extract (PFE) on N-formyl-Met-Leu-Phe (fMLF)-stimulated human neutrophils and the underlying mechanisms. PFE (1, 3, and 10 µg/ml) inhibited superoxide anion production, elastase release, reactive oxygen species formation, CD11b expression, and cell migration in fMLF-activated human neutrophils in dose-dependent manners. PFE inhibited fMLF-induced phosphorylation of the Src family kinases (SFKs), Src (Tyr416) and Lyn (Tyr396), and reduced their enzymatic activities. Both PFE and PP2 (a selective inhibitor of SFKs) reduced the phosphorylation of Burton's tyrosine kinases (Tyr223) and Vav (Tyr174) in fMLF-activated human neutrophils. Additionally, PFE decreased intracellular Ca(2+) levels ([Ca(2+)]i), whereas PP2 prolonged the time required for [Ca(2+)]i to return to its basal level. Our findings indicated that PFE effectively regulated the inflammatory activities of fMLF-activated human neutrophils. The anti-inflammatory effects of PFE on activated human neutrophils were mediated through two independent signaling pathways involving SFKs (Src and Lyn) and mobilization of intracellular Ca(2+).

Osthol attenuates neutrophilic oxidative stress and hemorrhagic shock-induced lung injury via inhibition of phosphodiesterase 4.

Oxidative stress caused by neutrophils is an important pathogenic factor in trauma/hemorrhagic (T/H)-induced acute lung injury (ALI). Osthol, a natural coumarin found in traditional medicinal plants, has therapeutic potential in various diseases. However, the pharmacological effects of osthol in human neutrophils and its molecular mechanism of action remain elusive. In this study, our data showed that osthol potently inhibited the production of superoxide anion (O2(•-)) and reactive oxidants derived therefrom as well as expression of CD11b in N-formylmethionylleucylphenylalanine (FMLP)-activated human neutrophils. However, osthol inhibited neutrophil degranulation only slightly and it failed to inhibit the activity of subcellular NADPH oxidase. FMLP-induced phosphorylation of extracellular signal-regulated kinase (ERK) and protein kinase B (Akt) was inhibited by osthol. Notably, osthol increased the cAMP concentration and protein kinase A (PKA) activity in activated neutrophils. PKA inhibitors reversed the inhibitory effects of osthol, suggesting that these are mediated through cAMP/PKA-dependent inhibition of ERK and Akt activation. Furthermore, the activity of cAMP-specific phosphodiesterase (PDE) 4, but not PDE3 or PDE7, was significantly reduced by osthol. In addition, osthol reduced myeloperoxidase activity and pulmonary edema in rats subjected to T/H shock. In conclusion, our data suggest that osthol has effective anti-inflammatory activity in human neutrophils through the suppression of PDE4 and protects significantly against T/H shock-induced ALI in rats. Osthol may have potential for future clinical application as a novel adjunct therapy to treat lung inflammation caused by adverse circulatory conditions.