Erk phosphorylation reduces the thymoquinone toxicity in human hepatocarcinoma

Molecular mechanisms and signaling pathways of black cumin (Nigella sativa) and its active constituent, thymoquinone: a review

BACKGROUND

Nigella sativa and its main bioactive ingredient, thymoquinone, exhibit various pharmacological activities, including neuroprotective, nephroprotective, cardioprotective, gastroprotective, hepatoprotective, and anti-cancer effects. Many studies have been conducted trying to elucidate the molecular signaling pathways that mediate these diverse pharmacological properties of N. sativa and thymoquinone. Accordingly, the goal of this review is to show the effects of N. sativa and thymoquinone on different cell signaling pathways.

METHODS

The online databases Scopus, PubMed and Web of Science were searched to identify relevant articles using a list of related keywords such as Nigella sativa, black cumin, thymoquinone, black seed, signal transduction, cell signaling, antioxidant, Nrf2, NF-κB, PI3K/AKT, apoptosis, JAK/STAT, AMPK, MAPK, etc. Only articles published in the English language until May 2022 were included in the present review article.

RESULTS

Studies indicate that N. sativa and thymoquinone improve antioxidant enzyme activities, effectively scavenges free radicals, and thus protect cells from oxidative stress. They can also regulate responses to oxidative stress and inflammation via Nrf2 and NF-κB pathways. N. sativa and thymoquinone can inhibit cancer cell proliferation through disruption of the PI3K/AKT pathway by upregulating phosphatase and tensin homolog. Thymoquinone can modulate reactive oxygen species levels in tumor cells, arrest the cell cycle in the G2/M phase as well as affect molecular targets including p53, STAT3 and trigger the mitochondrial apoptosis pathway. Thymoquinone, by adjusting AMPK, can regulate cellular metabolism and energy hemostasis. Finally, N. sativa and thymoquinone can elevate brain GABA content, and thus it may ameliorate epilepsy.

CONCLUSIONS

Taken together, the improvement of antioxidant status and prevention of inflammatory process by modulating the Nrf2 and NF-κB signaling and inhibition of cancer cell proliferation through disruption of the PI3K/AKT pathway appear to be the main mechanisms involved in different pharmacological properties of N. sativa and thymoquinone.

The Cytotoxic Effect of Thymoquinone Enhance on HepG2 Cell Line due to Induction of Fenton Reaction by Hydrogen Peroxide: An In Vitro and In Silico Study

OBJECTIVE

Thymoquinone (TQ) is a component derived from the volatile oil of Nigella sativa. Fenton reaction induction is a well-known strategy to prevent the growth of cancer cells which can stimulate by hydrogen peroxide. This study was designed to investigate the TQ effects on hydrogen peroxide-induced cytotoxicity.

METHODS

In this study, HepG2 cell survival, reactive oxygen species (ROS) production, cell membrane integrity, and changes of superoxide dismutase (SOD)/ catalase (CAT) activity were evaluated following incubation of HepG2 cells with 31 μM hydrogen peroxide and different concentrations of TQ (18.5, 37 and 75 μM). In addition, molecular docking studies on the interference of TQ with CAT/SOD enzymes were investigated.

RESULTS

Our findings showed that TQ low concentration can increase the survival of HepG2 cells when exposed to hydrogen peroxide, and on the contrary, its high concentration can potentiate cytotoxicity induced by hydrogen peroxide. The TQ alongside hydrogen peroxide increased the production of ROS, which was related to increase CAT and SOD activity in the HepG2 cells. Molecular docking findings showed that TQ effects on the formation of free radicals were not related to its chemical interference with the structure of the SOD/CAT molecules.

CONCLUSION

Fenton reaction induction may increase the effectiveness of TQ in preventing HepG2 cells proliferation.

Thymoquinone induces apoptosis in temozolomide-resistant glioblastoma cells via the p38 mitogen-activated protein kinase signaling pathway

Temozolomide (TMZ) can cross the blood-brain barrier (BBB) and deliver methyl groups to the purine (guanine) bases of DNA, leading to mispairing during DNA replication and subsequent cell death. However, increased expression of the repair enzyme methyl guanine methyltransferase (MGMT), which removes methyl groups from purine bases, counteracts methylation by TMZ. We evaluated the anticancer potential of thymoquinone (TQ), a hydrophobic flavonoid that inhibits resistance and induces apoptosis in various cancer cells, both in vitro and in vivo. In vitro experiments showed that compared with the Hs683 and M059J cell lines, U251 cells were more sensitive to TMZ. Compared to U251 cells, U251R cells, a TMZ drug-resistant strain established in this study, are characterized by increased expression of phosphorylated extracellular signal-regulated kinase (p-ERK) and MGMT. TQ treatments induced apoptosis in all cell lines. The p38 mitogen-activated protein kinase signal pathway was mainly activated in U251 and U251R cells; however, p-ERK and MGMT upregulation could not suppress TQ effects. Furthermore, si-p38 pretreatment of U251R cells in TQ treatments inhibited cell apoptosis. We speculate that TQ contributed to the phosphorylation and activation of p38, but not of ERK-induced apoptosis (irrespective of TMZ resistance). In vivo, U251R-derived tumors subcutaneously inoculated in nude mice exhibited significant tumor volume reduction after TQ or TQ + TMZ cotreatments. High-performance liquid chromatography assay confirmed the presence of TQ in murine brain tissues. Our findings demonstrate that TQ can effectively cross the BBB and function alone or in combination with TMZ to treat glioblastoma.

Biological Potential of the Main Component, Thymoquinone, of Nigella sativa in Pulp Therapy-In Vitro Study

This work is designed to assess the antimicrobial efficacy, chelating efficacy, and dissolving capability of the bioactive agent of the Nigella sativa plant (thymoquinone). Four freeze-dried microorganisms were studied. Each species was treated with either 6% sodium Hypochlorite, thymoquinone, or sterile water. The zone of inhibition was measured. Thirty extracted human premolar teeth were utilized to evaluate the smear layer removal. Root canals were mechanically instrumented and then irrigated with either 6% sodium Hypochlorite, 17% ethylenediaminetetraacetic acid, or thymoquinone for 1 min and scanned under the scanning electron microscopic to evaluate the cleanliness of the root canal and the remainder of the smear layer. To evaluate the tissue dissolving effect, Bovine Pulp Tissue was utilized. Randomly treated samples included: 6% sodium Hypochlorite, thymoquinone, or isotonic saline for 30 min. The remaining pulp tissue was weighed. Thymoquinone reported the highest inhibition of microbial multiplication compared to other irrigants (p < 0.001). Thymoquinone solution had an excellent antibacterial effect on endodontic pathogen and did not affect the inorganic and organic tissue inside the root canal. Meanwhile, it reported weak chelating and dissolving effects. Tissue dissolution was statistically significant with sodium Hypochlorite solution compared to other groups (p < 0.001).

The Role of Thymoquinone in Inflammatory Response in Chronic Diseases

Anti-inflammatory therapies have been shown to be effective in the prevention of various cardiovascular diseases, tumors, and cancer complications. Thymoquinone (TQ), the main active constituent of Nigella sativa, has shown promising therapeutic properties in many in vivo and in vitro models. However, TQ has poor bioavailability and is hydrophobic, prohibiting clinical trials with TQ alone. Studies have explored the combination of TQ with biological nanomaterials to improve its bioavailability. The TQ nanoparticle formulation shows better bioavailability than free TQ, and these formulations are ready for clinical trials to determine their potential as therapeutic agents. In this paper, we review current knowledge about the interaction between TQ and the inflammatory response and summarize the research prospects in Korea and abroad. We discuss the different biological activities of TQ and various combination therapies of TQ and nanomaterials in clinical trials.

Nigella sativa L. Phytochemistry and Pharmacological Activities: A Review (2019-2021)

Medicinal and aromatic plants are mainly characterized by the presence of different bioactive compounds which exhibit various therapeutic activities. In order to investigate the different pharmacological properties of different Nigella sativa extracts, a multitude of research articles published in the period between 2019 and 2021 were obtained from different databases (Scopus, Science Direct, PubMed, and Web of Science), and then explored and analyzed. The analysis of the collected articles allows us to classify the phytochemicals and the pharmacological activities through their underlying molecular mechanisms, as well as to explore the pharmacological activities exhibited by several identified compounds in Nigella sativa which allow a better understanding, and better elucidation, of the bioactive compounds responsible for the pharmacological effects. Also shown are the existence of other bioactive compounds that are still unexplored and could be of great interest. This review could be taken as a guide for future studies in the field.