Combating Staphylococcus aureus biofilm formation: the inhibitory potential of tormentic acid and 23-hydroxycorosolic acid

Plant extracts have been used to treat microbiological diseases for centuries. This study examined plant triterpenoids tormentic acid (TA) and 23-hydroxycorosolic acid (HCA) for their antibiofilm effects on Staphylococcus aureus strains (MTCC-96 and MTCC-7405). Biofilms are bacterial colonies bound by a matrix of polysaccharides, proteins, and DNA, primarily impacting healthcare. As a result, ongoing research is being conducted worldwide to control and prevent biofilm formation. Our research showed that TA and HCA inhibit S. aureus planktonic growth by depolarizing the bacterial membrane. In addition, zone of inhibition studies confirmed their effectiveness, and crystal violet staining and biofilm protein quantification confirmed their ability to prevent biofilm formation. TA and HCA exhibited substantial reductions in biofilm formation for S. aureus (MTCC-96) by 54.85% and 48.6% and for S. aureus (MTCC-7405) by 47.07% and 56.01%, respectively. Exopolysaccharide levels in S. aureus biofilm reduced significantly by TA (25 μg/mL) and HCA (20 μg/mL). Microscopy, bacterial motility, and protease quantification studies revealed their ability to reduce motility and pathogenicity. Furthermore, TA and HCA treatment reduced the mRNA expression of S. aureus virulence genes. In silico analysis depicted a high binding affinity of triterpenoids for biofilm and quorum-sensing associated proteins in S. aureus, with TA having the strongest affinity for TarO (- 7.8 kcal/mol) and HCA for AgrA (- 7.6 kcal/mol). TA and HCA treatment reduced bacterial load in S. aureus-infected peritoneal macrophages and RAW264.7 cells. Our research indicates that TA and HCA can effectively combat S. aureus by inhibiting its growth and suppressing biofilm formation.

Tormentic acid inhibits hepatic stellate cells activation via blocking PI3K/Akt/mTOR and NF-κB signalling pathways

The present study was to investigate the inhibitory effect and underlying mechanism of Tormentic acid (TA) on hepatic stellate cells (HSCs). HSC-T6 cells were stimulated with Platelet-derived growth factor-BB (PDGF-BB) and TA, and then cell proliferation, apoptosis, inflammatory factor, and collagen-related indicators were detected. In order to elucidate the potential mechanism, the PI3K/Akt/mTOR and NF-κB signalling pathways were also detected. The results showed that TA treatment markedly inhibited PDGF-BB-stimulated HSC-T6 cell activation, as evidenced by the inhibition of cell proliferation, migration and colony formation, as well as the decreased expression of TGF-β and α-SMA. TA treatment caused a significant increase in the activity of lactate dehydrogenase and significantly promoted cell apoptosis. TA treatment significantly reduced aspartate aminotransferase, alanine aminotransferase and total bilirubin activity. Importantly, TA inhibited the expression of collagen type I and III, alleviating the excessive deposition of extracellular matrix (ECM). Further experiments showed that TA administration significantly inhibited the phosphorylation of PI3K, Akt, FAK and mTOR and the protein expression of P70S6K, indicating the inhibition of the PI3K/Akt/mTOR pathway. Moreover, treatment with TA markedly decreased the phosphorylation of IκBα, NF-κB p65 and IKKα/β, thereby blocking the NF-κB signal transduction. In summary, this study demonstrates that TA significantly inhibits HSC activation and promotes cell apoptosis via the inhibition of the PI3K/Akt/mTOR and NF-κB signalling pathways. SIGNIFICANCE OF THE STUDY: Tormentic acid (TA) could inhibit HSC activation and alleviate collagen-based ECM deposition, suggesting that TA exerted anti-hepatic fibrosis. Further mechanism research revealed that the inhibition of TA on HSC activation might be through blocking the PI3K/Akt/mTOR and NF-κB signalling pathways. These findings provided a new cue to understand the protective effect of TA against liver fibrosis, which may provide a potential nature medicine for the treatment of liver fibrosis.

Tormentic acid confers protection against oxidative stress injury in rats with Parkinson's disease by targeting the Wnt/β-catenin signaling pathway

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). Studies have shown that oxidative stress (OS) may contribute to the cascade of reactions leading to the degeneration of dopaminergic neurons in the brain. The present study investigated the protective effect of tormentic acid (TMA) on OS-induced injury in rat model of PD, and the underlying mechanism. Evaluation of learning and memorizing ability was done using Morris water maze (MWM) test. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx), and level of malondialdehyde (MDA) in substantia nigra were determined using enzyme-linked immunosorbent assay (ELISA). The protein and mRNA expressions of β-catenin, GSK-3β, and GSK-3β-Ser9 were determined using real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting. The effect of TA on cell viability and proliferation was determined in vitro on rat adrenal pheochromocytoma (PC12) cell line using MTT assay. The results showed that the escape latency of rats in negative control group was significantly higher than that in normal control group (p < 0.05). However, treatment with TMA significantly and time-dependently reduced the escape latency of the rats (p < 0.05). The extent of apoptosis was significantly  reduced after treatment with TMA (p < 0.05). Besides, treatment with TMA significantly increased the viability of brain cells (p < 0.05). The activities of SOD and GPx were significantly lower in negative control group than in normal control group, but were significantly increased after treatment with TMA (p < 0.05). The level of MDA was significantly higher in negative control group than in normal control group, but was significantly reduced after treatment with TMA (p < 0.05). The results of qRT-PCR and Western blotting showed that treatment with TMA significantly activated Wnt/β-catenin signaling pathway (p < 0.05). TMA treatment significantly reversed the effect of 6-hydroxydopamine on the expression levels of these proteins and their mRNAs (p < 0.05). These results suggest that TMA confers protection against OS-induced injury in rats with PD by targeting the Wnt/β-catenin signaling pathway.

Euscaphic acid and Tormentic acid protect vascular endothelial cells against hypoxia-induced apoptosis via PI3K/AKT or ERK 1/2 signaling pathway

AIMS

Euscaphic acid and Tormentic acid are aglycones of Kaji-ichigoside F1 and Rosamultin, respectively. These four compounds are pentacyclic triterpenoid, isolated from the subterranean root of the Potentilla anserina L. Based on the protective roles against hypoxia-induced apoptosis of Euscaphic acid and Tormentic acid in vascular endothelial cells, this study was designed to determine the mechanisms.

MAIN METHODS

The model of hypoxic injuries in EA. hy926 cells was established. Through applications of PI3K/AKT inhibitor, LY294002 and ERK1/2 inhibitor, PD98059, we explored the relationships between pharmacodynamic mechanisms and PI3K/AKT or ERK 1/2 signaling pathway. The anti-hypoxic effects were studied by methyl-thiazolyl-tetrazolium (MTT) assay, Hematoxylin-Eosin (HE) staining, DAPI staining, and flow cytometry. The mechanisms of anti-mitochondrial apoptosis were explored by western blot. The expressions of p-ERK 1/2, ERK 1/2, p-AKT, AKT, p-NF-κB, NF-κB, Bcl-2, Bax, Cyt C, cleaved caspase-9 and cleaved caspase-3 were detected.

KEY FINDINGS

Euscaphic acid protected vascular endothelial cells against hypoxia-induced apoptosis via ERK1/2 signaling pathway, and Tormentic acid brought its efficacy into full play via PI3K/AKT and ERK1/2 signaling pathways. In addition, PI3K/AKT signaling pathway positively regulated ERK1/2 pathway, and ERK1/2 pathway negatively regulated PI3K/AKT pathway.

SIGNIFICANCE

This evidence provides theoretical and experimental basis for the following research on anti-hypoxic drugs of Potentilla anserina L.

The anti-biofilm potential of triterpenoids isolated from Sarcochlamys pulcherrima (Roxb.) Gaud

Formation of biofilm is the major cause of Pseudomonas aeruginosa associated pathological manifestations in the urinary tract, respiratory system, gastrointestinal tract, skin, soft tissues etc. Triterpenoid group of compounds have shown their potential in reducing planktonic and biofilm form of bacteria. Sarcochlamys pulcherrima (Roxb.) Gaud. is an ethnomedicinal plant traditionally used for its anti-microbial and anti-inflammatory property. In the present study two triterpenoids, have been isolated from this plant, characterised and evaluated for their antibacterial and antibiofilm potential against P. aeruginosa. Compounds were characterised as 2α, 3β, 19α-trihydroxy-urs-12-ene-28-oic acid (Tormentic acid) and 2α, 3β, 23-trihydroxyurs-12-ene-28-oic acid (23-hydroxycorosolic acid) through spectroscopic studies viz. infrared (IR), nuclear magnetic resonance (NMR) and mass spectroscopy (MS). Depolarization of bacterial membrane and zone of inhibition studies revealed that both the compounds inhibited the growth of planktonic bacteria. Compounds were also found to inhibit the formation of P. aeruginosa biofilm. Inhibition of biofilm found to be mediated through suppressed secretion of pyoverdin, protease and swarming motility of P. aeruginosa. Gene expression study, in silico binding analysis, in vivo bacterial load and tissue histology observations also supported the antibiofilm activity of both the compounds. In vitro and in vivo study showed that both compounds were non-toxic. The study has explored the antibacterial and antibiofilm effect of two triterpenes isolated for the first time from S. pulcherrima.

Protection against MPP(+)-induced neurotoxicity in SH-SY5Y cells by tormentic acid via the activation of PI3-K/Akt/GSK3β pathway

The cause of Parkinson's disease (PD) could be ascribed to the progressive and selective loss of dopaminergic neurons in the substantia nigra pars compacta, and thus molecules with neuroprotective ability may have therapeutic value against PD. In the current study, the neuroprotective effects and underlying mechanisms of tormentic acid (TA), a naturally occurring triterpene extracted from medicinal plants such as Rosa rugosa and Potentilla chinensis, were evaluated in a widely used cellular PD model in which neurotoxicity was induced by MPP(+) in cultured SH-SY5Y cells. We found that TA at 1-30 μM substantially protected against MPP(+)-induced neurotoxicity, as evidenced by the increase in cell viability, decrease in lactate dehydrogenase release and the reduction in apoptotic nuclei. Moreover, TA effectively inhibited the elevated intracellular accumulation of reactive oxygen species as well as Bax/Bcl-2 ratio caused by MPP(+). Most importantly, TA markedly reversed the inhibition of protein expression of phosphorylated Akt (Ser 473) and phosphorylated GSK3β (Ser 9) caused by MPP(+). LY294002, the specific inhibitor of PI3-K, significantly abrogated the up-regulated phosphorylated Akt and phosphorylated GSK3β offered by TA, suggesting that the neuroprotection of TA was mainly dependent on the activation of PI3-K/Akt/GSK3β signaling pathway. The results taken together indicate that TA may be a potential candidate for further preclinical study aimed at the prevention and treatment of PD.

Tormentic acid inhibits LPS-induced inflammatory response in human gingival fibroblasts via inhibition of TLR4-mediated NF-κB and MAPK signalling pathway

OBJECTIVE

Periodontal disease is one of the most prevalent oral diseases, which is associated with inflammation of the tooth-supporting tissues. Tormentic acid (TA), a triterpene isolated from Rosa rugosa, has been reported to exert anti-inflammatory effects. The aim of this study was to investigate the anti-inflammatory effects of TA on lipopolysaccharide (LPS)-stimulated human gingival fibroblasts (HGFs).

METHODS

The levels of inflammatory cytokines such as interleukin (IL)-6 and chemokines such as IL-8 were detected by enzyme-linked immunosorbent assay (ELISA). The expression of Toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), IκBα, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) was determined by Western blotting.

RESULTS

The results showed that Porphyromonas gingivalis LPS significantly upregulated the expression of IL-6 and IL-8. TA inhibited the LPS-induced production of IL-6 and IL-8 in a dose-dependent manner. Furthermore, TA inhibited LPS-induced TLR4 expression; NF-κB activation; IκBα degradation; and phosphorylation of ERK, JNK, and P38.

CONCLUSION

TA inhibits the LPS-induced inflammatory response in HGFs by suppressing the TLR4-mediated NF-κB and mitogen-activated protein kinase (MAPK) signalling pathway.

Anti-inflammatory activities of tormentic acid from suspension cells of Eriobotrya Japonicaex vivo and in vivo

Anti-inflammatory effects of tormentic acid (TA) were investigated ex vivo and in vivo. TA decreased the paw edema at the 4th and 5thhour after λ-carrageenin (Carr) administration, and increased the activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in the liver tissue. TA also significantly attenuated the thiobarbituric acid reactive substances (TBARS) level in the edematous paw at the 5thhour after Carr injection. TA decreased the nitric oxide (NO) levels on the serum level and diminished the serum tumour necrosis factor (TNF-α) at the 5thhour after Carr injection. Western blotting revealed that the TA decreased Carr-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions. As per results, the anti-inflammatory mechanisms of TA might be correlated to the decrease in the level of TBARS, iNOS, and COX-2 in the edema paw via increasing the activities of CAT, SOD, and GPx in the liver.