Tetrandrine

A Comprehensive Review about the Molecular Structure of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): Insights into Natural Products against COVID-19

In 2019, the world suffered from the emergence of COVID-19 infection, one of the most difficult pandemics in recent history. Millions of confirmed deaths from this pandemic have been reported worldwide. This disaster was caused by SARS-CoV-2, which is the last discovered member of the family of Coronaviridae. Various studies have shown that natural compounds have effective antiviral properties against coronaviruses by inhibiting multiple viral targets, including spike proteins and viral enzymes. This review presents the classification and a detailed explanation of the SARS-CoV-2 molecular characteristics and structure-function relationships. We present all currently available crystal structures of different SARS-CoV-2 proteins and emphasized on the crystal structure of different virus proteins and the binding modes of their ligands. This review also discusses the various therapeutic approaches for COVID-19 treatment and available vaccinations. In addition, we highlight and compare the existing data about natural compounds extracted from algae, fungi, plants, and scorpion venom that were used as antiviral agents against SARS-CoV-2 infection. Moreover, we discuss the repurposing of select approved therapeutic agents that have been used in the treatment of other viruses.

Lysosomal TPCN (two pore segment channel) inhibition ameliorates beta-amyloid pathology and mitigates memory impairment in Alzheimer disease

ABBREVIATIONS

Aβ: β-amyloid; AD: Alzheimer disease; AIF1/IBA1: allograft inflammatory factor 1; ALP: autophagy-lysosomal pathway; APP: amyloid beta precursor protein; ATP6V1B1/V-ATPase V1b1: ATPase H+ transporting V1 subunit B1; AVs: autophagy vacuoles; BAF: bafilomycin A₁; CFC: contextual/cued fear conditioning assay; CHX: Ca²⁺/H⁺ exchanger; CTF-β: carboxy-terminal fragment derived from β-secretase; CTSD: cathepsin D; fAD: familial Alzheimer disease; GFAP: glial fibrillary acidic protein; LAMP1: lysosomal associated membrane protein 1; LTP: long-term potentiation; MCOLN1/TRPML1: mucolipin 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPT: microtubule associated protein tau; MWM: Morris water maze; NFT: neurofibrillary tangles; PFC: prefrontal cortex; PSEN1: presenilin 1; SQSTM1/p62: sequestosome 1; TBS: theta burst stimulation; TEM: transmission electronic microscopy; TPCN2/TPC2: two pore segment channel 2; WT: wild-type; V-ATPase: vacuolar type H⁺-ATPase.

Challenges and future directions of potential natural products leads against 2019-nCoV outbreak

Except for Remdesivir® no other drug or vaccine has yet been approved to treat the coronavirus disease (COVID-19) caused by the virus known as, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Remdesivir® an small molecule and nucleic acid analogue, it is used to treat adults and children with laboratory confirmed COVID-19, only administrated in hospital settings. Small molecules and particularly natural products count for almost fifty percent of the commercially available drugs, several of them are marketed antiviral agents and those can be a potential agent to treat COVID-19 infections. This short review rationalized different key natural products with known activity against coronaviruses as potential leads against COVID-19.

Pharmacological hypothesis: TPC2 antagonist tetrandrine as a potential therapeutic agent for COVID-19

More than ten million patients worldwide have been diagnosed with coronavirus disease 19 (COVID-19) to date (WHO situation report, 1st July 2020). There is no vaccine to prevent infection with the causative organism, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), nor a cure. In the struggle to devise potentially useful therapeutics in record time, the repurposing of existing compounds is a key route of action. In this hypothesis paper, we argue that the bisbenzylisoquinoline and calcium channel blocker tetrandrine, originally extracted from the plant Stephania tetrandra and utilized in traditional Chinese medicine, may have potential in the treatment of COVID-19 and should be further investigated. We collate and review evidence for tetrandrine's putative mechanism of action in viral infection, specifically its recently discovered antagonism of the two-pore channel 2 (TPC2). While tetrandrine's particular history of use provides a very limited pharmacological dataset, there is a suggestion from the available evidence that it could be effective at doses used in clinical practice. We suggest that further research to investigate this possibility should be conducted.

Synthesis of 5-Alkynyltetrandrine Derivatives and Evaluation of their Anticancer Activity on A549 Cell Lines

BACKGROUND

Lung cancer is one of the most prevalent malignancies and thus the development of novel therapeutic agents for managing lung cancer is imperative. Tetrandrine, a bis-benzyltetrahydroisoquinoline alkaloid isolated from Stephania tetrandra S. Moore, has been found to exert cytotoxic effects on cancerous cells.

METHODS

A series of 5-alkynyltetrandrine derivatives was synthesized via the Sonogashira cross-coupling reactions and evaluated as potential anti-tumor agents. The anti-tumor activities of 12 compounds on lung cancer cells (A549) were evaluated using the MTT method. The population of apoptotic cells was measured using a TUNEL assay. Real-time PCR quantified the gene expression levels of Bcl-2, Bax, survivin and caspase-3. The content of Cyt-C was detected using a Human Cyt-C ELISA kit.

RESULTS

Most of these compounds exhibited better activities than tetrandrine itself on A549 cells. Among them, compound 7 showed the highest cytotoxicity among the tested compounds against human lung adenocarcinoma A549 cells with an IC50 of 2.94 µM. Preliminary mechanistic studies indicated that compound 7 induced apoptosis of human lung cancer A549 cells and increased the level of the proapoptotic gene Bax, release of Cyt-C from mitochondria and activation of caspase-3 genes.

CONCLUSION

The results suggest that compound 7 exerts its antitumor activity against A549 cells through the induction of the intrinsic (mitochondrial) apoptotic pathway. These findings will contribute to the future design of more effective anti-tumor agents in lung cancer therapy.

Self-Nanoemulsifying Drug Delivery System of Tetrandrine for Improved Bioavailability: Physicochemical Characterization and Pharmacokinetic Study

The main purpose of this study was to investigate the potential of self-nanoemulsified drug delivery system (SNEDDS) to improve the oral bioavailability of tetrandrine (Tet). SNEDDS was developed by using rational blends of excipients with good solubilizing ability for Tet which was selected based on solubility studies. Further ternary phase diagram was constructed to determine the self-emulsifying region. The optimal formulation with the best self-nanoemulsified and solubilization ability consisted of 40% (w/w) oleic acid as oil, 15% (w/w) SPC and 30% (w/w) Cremophor RH-40 as surfactant, and 15% (w/w) PEG₄₀₀ as cosurfactant. The average droplet size and zeta-potential of the optimal Tet SNEDDS were 19.75±0.37 nm and 1.87±0.26 mv, respectively. The dissolute rate of Tet SNEDDS in various dissolution media was remarkably faster than Tet commercial tablet. Moreover, in vivo pharmacokinetic study results show that significant increase (p≤ 0.05) in the peak concentration (Cmax) and the area under the curve (AUC) of Tet was observed after the oral administration of Tet SNEDDS and the absorption of Tet from SNEDDS resulted in approximately 2.33-fold increase in oral bioavailability compared with the commercial tablet. Our research suggests that the prepared Tet SNEDDS could be a good candidate for improved the dissolution and oral bioavailability of Tet.

Design and synthesis of novel C14-urea-tetrandrine derivatives with potent anti-cancer activity

Tetrandrine is a dibenzyltetrahydroisoquinoline alkaloid, isolated from traditional Chinese medicinal plant Stephania tetrandra, with anti-tumor activity. Our previous study identified several derivatives of tetrandrine showing better activities than parental compound against human hepatocellular carcinoma cells. To increase diversity and cytotoxic activities of the original compound, a series of novel 14-urea-tetrandrine derivatives were synthesized through structural modification of tetrandrine. These derivaties demonstrated a moderate to strong anti-proliferative activities against human cell lines HEL and K562 (Leukemia), prostate (PC3), breast (MDA-MB-231) and melanoma (WM9). Compound 4g showed strongest cytotoxic effect against PC3 cells with IC₅₀ value of 0.64 μM, which was 12-fold, 31-fold and 26-fold lower than the parental tetrandrine, 5-fluorouracil and cisplatin, respectively. Preliminary structure-activity relationship study indicated that urea subsititution was the key pharmacophore for the enhancement of their antitumor activities. Induction of apoprosis by 4g was associated with the activation of pro-apoptotic protein BAX and inhibition of antiapoptosis proteins survivin as well as Bcl-2. Moreover, activation of caspases led to increase cleavage of PARP, which further accelerates apoptotic cell death. These results reveal that the compound 4g may be used as a potential anticancer drug candidate.

Tetrandrine and cancer - An overview on the molecular approach

Tetrandrine has been known in the treatment of tuberculosis, hyperglycemia, negative ionotropic and chronotropic effects on myocardium, malaria, cancer and fever since years together. It has been known that, tetrandrine could modulate multiple signaling molecules such as kinases of cell cycle and rat sarcoma (RAS) pathway along with proteins of tumor suppressor genes, autophagy related, β-catenins, caspases, and death receptors. Moreover, tetrandrine exhibited reversal of drug resistance by modulating P-glyco protein (P-gp) expression levels in different cancers which is an added advantage of this compound compared to other chemotherapy drugs. Though, bioavailability of tetrandrine is a limiting factor, the anticancer activity was observed in animal models without changing any pharmacokinetic parameters. In the present review, role of tetrandrine as kinase inhibitor, inducer of autophagy and caspase pathways and suppressor of RAS mediated cell proliferation were discussed along with inhibition of angiogenesis. It has also been discussed that how tetrandrine potentiate anticancer effect in different types of cancers by modulating multidrug resistance under in vitro and in vivo trials including the available literature on the clinical trials.

Tetrandrine--A molecule of wide bioactivity

Stephania tetrandra and other related species of Menispermaceae form the major source of the bisbenzylisoquinoline alkaloid - tetrandrine. The plant is extensively referenced in the Chinese Pharmacopoeia for its use in the Chinese medicinal system as an analgesic and diuretic agent and also in the treatment of hypertension and various other ailments, including asthma, tuberculosis, dysentery, hyperglycemia, malaria, cancer and fever. Tetrandrine, well-known to act as a calcium channel blocker, has been tested in clinical trials and found effective against silicosis, hypertension, inflammation and lung cancer without any toxicity. Recently, the efficacy of tetrandrine was tested against Mycobaterium tuberculosis, Candida albicans, Plasmodium falciparum and Ebola virus. Tetrandrine's pharmacological property has been proved to be through its action on different signalling pathways like reactive oxygen species, enhanced autophagic flux, reversal of multi drug resistance, caspase pathway, cell cycle arrest and by modification of calcium channels. The present review summarises current knowledge on the synthesis, distribution, extraction, structural elucidation, pharmacological properties and the mechanism of action of tetrandrine. Future perspectives in the clinical use of tetrandrine as a drug are also considered.

The plasma glucose lowering action of tetrandrine in streptozotocin-induced diabetic rats

The effect of tetrandrine, an active principle of Stephaniae tetrandrae, on the plasma glucose level in streptozotocin-induced diabetic rats (STZ-diabetic rats) was investigated. A single intravenous injection of tetrandrine decreased the plasma glucose in a dose-dependent manner in STZ-diabetic rats. Moreover, tetrandrine (1.0 mg kg−1) significantly attenuated the rise in plasma glucose induced by the intravenous glucose challenge test in normal rats. A stimulatory effect of tetrandrine on glucose uptake was obtained in soleus muscles isolated from STZ-diabetic rats with a concentration-dependent manner from 0.01 to 10.0 μmol L−1. The increase in glucose utilization by tetrandrine was further characterized using the enhancement of glycogen synthesis in the hepatocytes of STZ-diabetic rats. These results suggest that tetrandrine has the ability to enhance glucose utilization in peripheral tissue, resulting in the lowering of plasma glucose in diabetic rats lacking insulin.

Stephania tetrandra prevents and regresses liver fibrosis induced by carbon tetrachloride in rats

BACKGROUND AND AIM

There is currently no safe and effective treatment for liver fibrosis. We have previously shown that Stephania tetrandra (ST) and Salvia miltiorrhiza (SM) suppress cell proliferation and enhance apoptosis of hepatic stellate cell (HSC) in vitro. In this study, we aimed to investigate the anti-fibrotic effect of these two herbs in vivo.

METHODS

Liver fibrosis was induced by carbon tetrachloride (CCl(4)) injection in rats for 5 weeks. SM, ST or SM + ST was gavaged on day 1 of CCl(4) administration to study the preventive effects of herbs on hepatic fibrosis. In a separate study designed to assess possible fibrosis regression, rats were randomly allocated to be treated with SM, ST or SM + ST when fibrosis was established. Liver injury and collagen content were assessed. HSC activation and apoptosis were determined.

RESULTS

As compared with the CCL(4)-only rats, serum ALT was significantly lower in CCl(4)-treated rats that received either SM (P < 0.01) or ST (P < 0.01). Administration of ST significantly prevented (P < 0.01) or reversed the hepatic fibrosis (P < 0.01) induced by CCL(4). Moreover, rats treated with ST had reduced protein expression of alpha-SMA both in prevention (P < 0.05) and in regression (P < 0.01) experiments. The double-color staining of alpha-SMA and TUNEL showed that ST increased HSC apoptosis. However, co-treatment of SM + ST did not increase the antifibrotic effect of ST.

CONCLUSIONS

Stephania tetrandra safely and effectively prevents and reverses hepatic fibrosis through activating HSC apoptosis in rats.

Anti-fibrotic effects of tetrandrine on bile-duct ligated rats

Tetrandrine (Tet) (C38H42O8N2; molecular weight, 622), an alkaloid isolated from the Chinese medicinal herb Stephania tetrandra, has been shown to elicit anti-inflammatory and anti-fibrotic effects in pulmonary diseases, but the mechanism of action has yet to be investigated. In this study, we tested whether Tet exerts anti-fibrotic effects on rat hepatic fibrosis through anti-NFkappaB pathways. After bile-duct ligation, rats were given Tet (1 or 5 mg/kg) or silymarin (50 mg/kg, as a positive control) by gavage twice daily for 3 weeks. Liver sections were taken for Sirius red quantitative scoring, immunofluorescence double staining of alpha-smooth muscle actin (alpha-SMA) and NFkappaB, and for quantitative determinations of the mRNA expression levels of TGF-beta1, alpha-SMA, collagen 1alpha2, inducible nitric oxide synthase (iNOS), intercellular adhesion molecule 1 (ICAM-1), metallothionein, vascular endothelial growth factor (VEGF), and VEGF type II receptor (VEGFR2) genes. The results showed that both Tet and silymarin treatment significantly reduced the fibrosis scores and hepatic collagen content of BDL rats, compared with no treatment. Both Tet and silymarin treatments decreased the number of alpha-SMA- and NFkappaB-positive cells in fibrotic livers. Moreover, Tet and silymarin treatments attenuated the mRNA expression levels of TGF-beta1,alpha-SMA, collagen 1alpha2, iNOS, ICAM-1, VEGF, and VEGFR2 genes, and induced the mRNA expression of the metallothionein gene. This study suggests that the anti-fibrotic effects of Tet were related to the reduction of fibrosis-related gene transcription, the attenuation of NFkappaB-activated pathways, and the induction of metallothionein gene transcription in the livers of BDL rats.

Antifibrotic effects of tetrandrine on hepatic stellate cells and rats with liver fibrosis

BACKGROUND

Anti-inflammation strategies are one of the proposed therapeutic approaches to hepatic fibrosis. Tetrandrine (C(38)H(42)O(8)N(2), molecular weight: 622; Tet), an alkaloid isolated from the Chinese medicinal herb Stephania tetrandra, has been shown to exert anti-inflammatory activity in pulmonary diseases. The purpose of the present study was to investigate the in vitro and in vivo effects of Tet on hepatic fibrosis.

METHODS

A cell line of rat hepatic stellate cells (HSC-T6) was stimulated with transforming growth factor-beta1 (TGF-beta1) or tumor necrosis factor-alpha (TNF-alpha). The inhibitory effects of Tet on the nuclear factor kappaB (NFkappaB) signaling cascade and molecular markers including intercellular adhesion molecule-1 (ICAM-1) and alpha-smooth muscle actin (alpha-SMA) secretion were assessed. Fibrosis was induced by dimethylnitrosamine (DMN) administration in rats for 4 weeks. Fibrotic rats were randomly assigned to one of the four groups: vehicle (0.7% carboxyl methyl cellulose, CMC), Tet (1 mg/kg), Tet (5 mg/kg), or silymarin (50 mg/kg), each given by gavage twice daily for 3 weeks starting after 1 week of DMN administration. At the end of the study, liver tissues were scored for fibrosis and analyzed for molecular markers of fibrosis.

RESULTS

Tetrandrine (0.5-5.0 micromol/L) concentration-dependently inhibited NFkappaB transcriptional activity induced by TNF-alpha, including IkappaBalpha phosphorylation and mRNA expressions of ICAM-1 in HSC-T6 cells. In addition, Tet also inhibited TGF-beta1-induced alpha-SMA secretion and collagen deposition in HSC-T6 cells. Fibrosis scores of livers from DMN-treated rats with high-dose Tet (1.3 +/- 0.3) were significantly reduced in comparison with DMN-treated rats receiving saline (2.0 +/- 0.2). Hepatic collagen content of DMN rats was significantly reduced by either Tet or silymarin treatment. Double-staining results showed that alpha-SMA- and NFkappaB-positive cells were decreased in the fibrotic livers by Tet and silymarin treatment. In addition, mRNA expression of ICAM-1, alpha-SMA, and TGF-beta1 was attenuated by Tet treatment. Moreover, levels of plasma aspartate aminotransferase and alanine aminotransferase activities were reduced by Tet and silymarin treatment.

CONCLUSION

Tetrandrine exerts antifibrotic effects in both HSC-T6 cells and in rats with DMN-induced fibrosis.

Inhibitory effects of tetrandrine on the serum- and platelet-derived growth factor-BB-induced proliferation of rat aortic smooth muscle cells through inhibition of cell cycle progression, DNA synthesis, ERK1/2 activation and c-fos expression

Tetrandrine (TET) is a well known naturally occurred nonspecific Ca(2+) channel blocker. It has long been used for the treatment of arrhythmia, hypertension, and occlusive cardiovascular disorders. The objective of the present study was to investigate the effect of TET on the proliferation of primary cultured rat aortic smooth muscle cells (RASMCs). TET significantly inhibited both 10% fetal bovine serum (FBS) and 50 ng/ml platelet-derived growth factor (PDGF)-BB-induced proliferation, [(3) H] ]thymidine incorporation into DNA, and p42/p44 mitogen-activated protein kinase (ERK1/2) phosphorylation at the concentration of 1.0 and 5.0 microM. Flow cytometry analysis of DNA content in synchronized cells revealed blocking of the FBS-inducible cell cycle progression by TET. In accordance with these findings, TET 5 microM caused a 48% decrease in the early elevation of c-fos expression induced after 10% FBS addition. Furthermore, in contrast to its distinguishable higher potency of Ca(2+) antagonistic activity, verapamil showed lower potent antiproliferative activities than TET. These results suggest that TET can exert antiproliferative effects against mitogenic stimuli for RASMCs in vitro by a mechanism that involves the MAPK pathway, altering cell cycle progression, and the inhibitory action cannot be limited to its Ca(2+) modulation.

Tetrandrine cytotoxicity and its dual effect on oxidative stress-induced apoptosis through modulating cellular redox states in Neuro 2a mouse neuroblastoma cells

Tetrandrine (TET), a plant alkaloid, is known primarily as a non-selective Ca(2+) channel blocker. On the contrary to the cytoprotective effect on ischemia/reperfusion injury, TET has also been reported to cause cytotoxicity. In this study, we wished to understand the apparently disparate effects of this potential drug and thus investigated molecular mechanisms on proliferation and apoptosis and its effect on oxidative stress-induced apoptosis in Neuro 2a mouse neuroblastoma cells. We showed that TET, at high concentrations, induced cell cycle arrest and apoptosis through oxidative stress with following observations. Firstly, 10 microM TET elevated the reactive oxygen species (ROS) level and accordingly depleted glutathione (GSH) content. Secondly, pretreatment with antioxidants (NAC or GSH) protected cells from TET-induced apoptosis. We also demonstrated that treatment with 10 microM TET caused not only induction of p53, p21(waf1), and Bax, but also nuclear translocation of p53 and hypo-phosphorylation of pRb concurrently. Our important finding is that the concentration-dependent dual effect of TET, either inhibiting or promoting cell death induced by H(2)O(2) was observed, probably through regulating redox balance, which was well reflected on the GSH content in each condition. Besides, inhibition of Ca(2+) influx protected cells from H(2)O(2)-induced apoptosis even in the presence of 10 microM TET. Taken together, our data suggest that TET regulation of cellular redox states may play a major role in its dual action of cytotoxicity and cytoprotection.

Tetrandrine ameliorates ischaemia-reperfusion injury of rat myocardium through inhibition of neutrophil priming and activation

1. We have previously shown that tetrandrine (TTD), a bisbenzyltetrahydroiosquinoline isolated from the Chinese herb Stephania tetrandra, inhibits neutrophil adhesion, Mac-1 expression, and reactive oxygen species (ROS) production. To examine whether inhibition of neutrophil function may confer upon TTD the ability to prevent myocardial ischaemia-reperfusion (MI/R) injury, experiments were performed on rats subjected to coronary ligation followed by reperfusion for induction of MI/R injury. 2. Intravenous administration of TTD (0.1 and 1.0 mg kg-1) 15 min prior to coronary ligation completely prevented MI/R-associated mortality. TTD pretreatment also significantly reduced MI/R-induced ventricular tachyarrhythmia, myocardial infarct size, and neutrophil infiltration. 3. However, TTD pretreatment did not influence mean arterial blood pressure, heart rate, or product of pressure-rate, indicating that TTD extenuated MI/R through mechanisms independent of modulating haemodynamics or myocardial oxygen demand. 4. Peripheral blood neutrophils were isolated for ex vivo examination of shape change and Mac-1 upregulation of neutrophils, two sensitive indicators of proinflammatory priming, as well as N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced adhesion and ROS production, parameters commonly used for the assessment of neutrophil activation. 5. Neutrophils from MI/R animals showed significant shape change and Mac-1 upregulation, both of which were prevented by TTD-pretreatments. On the other hand, fMLP-induced adhesion and ROS production of neutrophils were markedly enhanced by MI/R but diminished in TTD-pretreated animals. 6. These data suggest that the protective effect of TTD against MI/R injury can be accounted for by inhibition of neutrophil priming and activation, thereby abolishing subsequent infiltration and ROS production that cause MI/R injury.