Methyl Gallate Improves Hyperuricemia Nephropathy Mice Through Inhibiting NLRP3 Pathway

Hyperuricemia nephropathy (HN) is a form of chronic tubulointerstitial inflammation, caused by the deposition of monosodium urate crystals (MSU) in the distal collecting duct and medullary interstitium, associated with a secondary inflammatory reaction. Numerous published reports indicated that NLRP3 inflammasome pathway play crucial roles in HN symptoms. The present study aims to investigate the protective effects of methyl gallate on HN mice and the underlying mechanisms. An HN model was established by intraperitoneal injection of potassium oxide (PO) to assess the effect of methyl gallate on renal histopathological changes, renal function, cytokine levels and expressions of NLRP3-related protein in HN mice. Moreover, in vitro models of lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs) and human peripheral blood mononuclear cells (PBMCs) were established to explore the mechanism of methyl gallate on NLRP3 inflammasome activation. The results showed that methyl gallate significantly ameliorated HN by inhibiting uric acid production and promoting uric acid excretion as well as ameliorating renal injury induced by NLRP3 activation. Mechanistically, methyl gallate is a direct NLRP3 inhibitor that inhibits NLRP3 inflammasome activation but has no effect on the activation of AIM2 or NLRC4 inflammasomes in macrophages. Furthermore, methyl gallate inhibited the assembly of NLRP3 inflammasomes by blocking the ROS over-generation and oligomerization of NLRP3. Methyl gallate was also active ex vivo against ATP-treated PBMCs and synovial fluid mononuclear cells from patients with gout. In conclusion, methyl gallate has a nephroprotective effect against PO-induced HN through blocking the oligomerization of NLRP3 and then exerting anti-inflammatory activity in the NLRP3-driven diseases.

Plicosepalus acacia Extract and Its Major Constituents, Methyl Gallate and Quercetin, Potentiate Therapeutic Angiogenesis in Diabetic Hind Limb Ischemia: HPTLC Quantification and LC-MS/MS Metabolic Profiling

Plicosepalus acacia (Fam. Loranthaceae) has been reported to possess hypoglycemic, antioxidant, antimicrobial, and anti-inflammatory effects. Liquid chromatography combined with tandem mass spectrometry (LC-MS/MS) analysis revealed the presence of a high content of polyphenolic compounds that are attributed to the therapeutic effects of the crude extract. In addition, methyl gallate and quercetin were detected as major phytomedicinal agents at concentrations of 1.7% and 0.062 g%, respectively, using high-performance thin layer chromatography (HPTLC). The present study investigated the effect of the P. acacia extract and its isolated compounds, methyl gallate and quercetin, on hind limb ischemia induced in type 1 diabetic rats. Histopathological examination revealed that treatment with P. acacia extract, methyl gallate, and quercetin decreased degenerative changes and inflammation in the ischemic muscle. Further biochemical assessment of the hind limb tissue showed decreased oxidative stress, increased levels of nitric oxide and endothelial nitric oxide synthase (eNOS), and enhancement of the levels of heme oxygenase-1 (HO-1) and vascular endothelial growth factor (VEGF) in the groups treated with methyl gallate and quercetin. Expression levels of hypoxia inducible factor-1 alpha (HIF-1α), VEGF, fibroblast growth factor-2 (FGF-2), and miR-146a were upregulated in the muscle tissue of methyl gallate- and quercetin-treated groups along with downregulation of nuclear factor kappa B (NF-κB). In conclusion, P. acacia extract and its isolated compounds, methyl gallate and quercetin, mediated therapeutic angiogenesis in diabetic hind limb ischemia.

Protective Effect of Methyl gallate on Murine Antigen-Induced Arthritis by Inhibiting Inflammatory Process and Bone Erosion

Methyl gallate (MG) is a plant-derived phenolic compound known to present remarkable anti-inflammatory effect in different experimental models such as paw oedema, pleurisy, zymosan-induced arthritis and colitis. Herein we investigated the effect of MG in the mice model of antigen-induced arthritis (AIA), a model with complex inflammatory response, driven primally by immune process and that cause bone and cartilage erosion similarly found in rheumatoid arthritis. Arthritis was induced by i.a injection of albumin methylated from bovine serum (mBSA) in C57BL/6 male mice previously immunized. The dose-response analysis of MG (0.7-70 mg/kg; p.o) showed that maximum inhibition was reached with the dose of 7 mg/kg on paw oedema and cell infiltration induced by AIA at 7 h. Treatment with MG (7mg/kg; p.o) or with the reference drug, dexamethasone (Dexa,10 mg/kg, ip) reduced AIA oedema formation, leukocyte infiltration, release of extracellular DNA and cytokine production 7 and 24 h (acute response). Mice treated daily with MG for seven days showed no significant weight loss or liver and kidney toxicity contrary to Dexa that induced some degree of toxicity. Prolonged treatment with MG inhibited the late inflammatory response (28 days) reducing oedema formation, cell infiltration, synovial hyperplasia, pannus formation and cartilage degradation as observed in histopathological analyses. Ultimately, MG reduced bone resorption as evidenced by a decrease in tartrate-resistant acid phosphate (TRAP)-positive cells number in femur histology. Altogether, we demonstrate that MG ameliorates the inflammatory reaction driven primarily by the immune process, suggesting a potential therapeutic application in arthritis treatment.

Paeonia lactiflora Root Extract and Its Components Reduce Biomarkers of Early Atherosclerosis via Anti-Inflammatory and Antioxidant Effects In Vitro and In Vivo

Although various physiological activities of compounds obtained from Paeonia lactiflora have been reported, the effects of P. lactiflora extract (PLE) on early atherosclerosis remain unclear. Therefore, in this study, we investigated the in vitro and in vivo antiatherosclerosis and in vitro antioxidant effects of PLE and its compounds. PLE suppresses the tumor necrosis factor (TNF)-α-induced capacity of THP-1 cells to adhere to human umbilical vein endothelial cells (HUVECs), vascular cell adhesion molecule (VCAM)-1 expression, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling in HUVECs. PLE also suppresses TNF-α-induced nuclear translocation of NF-κB p65 from cytosol as well as the enhanced TNFA and C-C motif chemokine ligand 2 (CCL2) mRNA expression in HUVECs. We identified and quantified the following PLE compounds using high-performance liquid chromatography with diode array detection: methyl gallate, oxypaeoniflorin, catechin, albiflorin, paeoniflorin, benzoic acid, benzoylpaeoniflorin, and paeonol. Among these, methyl gallate had the strongest inhibitory effect on monocyte adherence to TNF-α-induced HUVECs and the VCAM-1 expression. Reverse transcriptase real-time quantitative polymerase chain reaction showed that PLE compounds had a dissimilar inhibition effect on TNF-α-induced mRNA expression levels of CCL2, TNFA, and IL6 in HUVECs. Except for paeonol, the compounds inhibited lipopolysaccharide (LPS)-induced reactive oxygen species production in RAW264.7 cells. In vivo, oral administration of PLE improved TNF-α-induced macrophage infiltration to the vascular endothelium and expression of VCAM-1, as well as IL6 and TNFA gene expression in the main artery of mice. PLE could be useful as a nutraceutical material against early atherosclerosis via the combined effects of its components.

The antioxidant methyl gallate inhibits fungal growth and deoxynivalenol production in Fusarium graminearum

Production of the Fusarium toxin deoxynivalenol (DON) is associated with oxidative stress and has been indicated to be part of an adaptive response to oxidative stress in the important wheat fungus Fusarium graminearum. In this study, we found that the antioxidant methyl gallate (MG) displays inhibitory effects against mycelial growth, conidial formation and germination, and DON biosynthesis in F. graminearum in a dose-dependent manner. Treatment with 0.05% (w/v) MG resulted in an abnormal swollen conidial morphology. The expression of the TRI genes involved in DON biosynthesis was significantly reduced, and the induction of Tri1-GFP green fluorescence signals in the spherical and crescent-shaped toxisomes was abolished in the MG-treated mycelium. RNA-Seq analysis of MG-treated F. graminearum showed that 0.5% (w/v) MG inhibited DON production by possibly altering membrane functions and oxidoreductase activities. Coupled with the observations that MG treatment decreases catalase, POD and SOD activity in F. graminearum. The results of this study indicated that MG displays antifungal activity against DON production by modulating its oxidative response. Taken together, the current study revealed the potential of MG in inhibiting mycotoxins in F. graminearum. Graphical abstract

A yceI Gene Involves in the Adaptation of Ralstonia solanacearum to Methyl Gallate and Other Stresses

Ralstonia solanacearum is a plant-pathogenic bacterium causing plant bacterial wilt, and can be strongly inhibited by methyl gallate (MG). Our previous transcriptome sequencing of MG-treated R. solanacearum showed that the yceI gene AVT05_RS03545 of Rs-T02 was up-regulated significantly under MG stress. In this study, a deletion mutant (named DM3545) and an over-expression strain (named OE3545) for yceI were constructed to confirm this hypothesis. No significant difference was observed among the growth of wild-type strain, DM3545, and OE3545 strains without MG treatment. Mutant DM3545 showed a lower growth ability than that of the wild type and OE3545 strains under MG treatment, non-optimal temperature, or 1% NaCl. The ability of DM3545 for rhizosphere colonization was lower than that of the wild-type and OE3545 strains. The DM3545 strain showed substantially reduced virulence toward tomato plants than its wild-type and OE3545 counterpart. Moreover, DM3545 was more sensitive to MG in plants than the wild-type and OE3545 strains. These results suggest that YceI is involved in the adaptability of R. solanacearum to the presence of MG and the effect of other tested abiotic stresses. This protein is also possibly engaged in the virulence potential of R. solanacearum.

Methyl Gallate Mitigates Doxorubicin-Induced Peripheral Cytopenias: A Preclinical Experimental Study

Myelosuppression by doxorubicin is a life-threatening adverse effect in cancer patients undergoing chemotherapy. Methyl gallate is an antioxidant found in a variety of plant species. The study aimed to demonstrate the protective role of methyl gallate on doxorubicin-induced cytopenias in Wistar rats. The animals were prophylactically treated with two different doses of methyl gallate (150mg/kg/day and 300mg/kg/day) orally for seven days. Doxorubicin (25mg/kg; single dose) was administered through intraperitoneal route on the seventh day to induce cytopenias. Blood was collected 24 hours after the administration of doxorubicin and complete blood counts were estimated. There was significant (p≤0.05) development of peripheral cytopenias in doxorubicin treated control rats compared to normal saline treated control rats. Methyl gallate at both the doses significantly (p≤0.05) mitigated doxorubicin induced cytopenias compared to doxorubicin treated control rats. The findings of the present study revealed that methyl gallate has protective role in doxorubicin-induced cytopenias in Wistar rats. Following clinical studies, methyl gallate may serve as a viable alternative to growth factors in patients undergoing chemotherapy.

ANTI-QUORUM SENSING AND ANTIBIOTIC ENHANCEMENT OF ALLYLPYROCATECHOL AND METHYL GALLATE

In this study, the antibiotic enhancement and quorum sensing (QS) inhibition of allylpyrocatechol (APC) and methyl gallate (MG) isolated from leaves of Piper betle (betel) and leaf shoots of Anacardium occidentale (cashew), respectively, were compared. When applied with streptomycin and tested against Staphylococcus aureus and Pseudomonas aeruginosa, the effect of APC was additive while that of MG was synergistic. In terms of QS inhibition against Chromobacterium violaceum, both compounds were equally effective with violacein inhibition observed at concentrations of 60 μg/mL. We successfully increased the purity of APC in the methanol betel leaf extract from 13.2% to 31.5% w/w through solvent partitioning. This study is the first to document the anti-QS activity of APC, which is comparable to that of MG.