Research Progress on the Biological Activities and Mechanisms of Action of Sulforaphane

Sulforaphane, also known as sulforaphane glucosinolate, is an isothiocyanate compound produced by the hydrolysis of glucosinolates under the action of endogenous myrosinase. It is widely found in cruciferous vegetables. Sulforaphane possesses antioxidant, antibacterial, and anti-inflammatory properties, and it is also one of the most potent anticancer components discovered in vegetables. Sulforaphane can induce apoptosis and cell cycle arrest in cancer cells, stimulate the production of phase II detoxifying enzymes in the human body, while inhibiting the production of phase I enzymes, ultimately eliminating carcinogens, free radicals, and other harmful components through various enzymatic systems.

1.Antioxidant Activity of Sulforaphane and Its Protective Mechanism against Oxidative Stress Cells

The antioxidant properties of sulforaphane are attributed to the interaction between its side chain groups and oxidants, rather than its direct involvement in redox reactions within the body. Studies have shown that sulforaphane can significantly increase the number and activity of phase II antioxidant enzymes, such as quinone reductase, GST (glutathione S-transferase), heme oxygenase, etc., enhancing the cell's ability to withstand oxidative stress and thereby effectively combating the damage caused by free radicals.

Studies have confirmed that sulforaphane exerts antioxidant effects in multiple organs and tissues of animals. Sulforaphane possesses high antioxidant activity and superoxide anion radical scavenging ability. By activating the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway, it enhances the binding of Nrf2 to DNA and increases promoter activity, restoring the expression level of peroxiredoxin 6 (Prdx6) recombinant protein, and stimulating the body to increase glutathione production, indirectly playing an antioxidant role. Sulforaphane's protection against oxidative stress can be achieved by reducing the methylation of the first 15 CpGs in the Nrf2 promoter, enhancing Nrf2 transcription, as well as by chemically modifying the cysteine residues (primarily Cys151) of Kelch-like ECH-associated protein 1 (Keap1) to prevent the binding of Keap1 and Nrf2, thereby blocking the ubiquitination and degradation of Nrf2. This leads to the accumulation of Nrf2 and the enhanced transcription of downstream genes regulated by Nrf2.

Furthermore, sulforaphane can increase the mRNA and protein expression of heme oxygenase-1 (HO-1), thereby reducing the level of reactive oxygen species (ROS) in mitochondria. In kidney injury models, sulforaphane has been shown to alleviate cisplatin (also known as cis-dichlorodiammineplatinum)-induced renal dysfunction, structural damage, and oxidative/nitrosative stress. Studies have found that sulforaphane can reduce cisplatin-induced mitochondrial mutations, alleviate the impairment of cellular protective enzymes such as quinone reductase 1 and γ-glutamylcysteine ligase activity, effectively prevent the increase in cisplatin-induced ROS, and mitigate nephrotoxic effects.

2.Antimicrobial Mechanism of Sulforaphane

Sulforaphane exhibits significant inhibitory effects against Escherichia coli, Staphylococcus aureus, Helicobacter pylori, and other microorganisms. Research has shown that sulforaphane inhibits Escherichia coli by affecting cell membrane permeability, cellular material and energy metabolism, and inhibiting nucleic acid and protein synthesis rates, with the inhibition of nucleic acid and protein synthesis being its primary antimicrobial mechanism. Western blot analysis indicates that Staphylococcus aureus activates the p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) signaling pathways, and the transcriptional levels of IL-1β, IL-6, and TNF-α genes are dependent on p38 and JNK. Pre-treatment with sulforaphane can prevent the phosphorylation of p38 and JNK, thereby effectively inhibiting food poisoning caused by Staphylococcus aureus.

Studies have found that when purified Helicobacter pylori urease is treated with sulforaphane, its UV absorption at 280-340 nm changes. With the extension of treatment time, dithiocarbamates can form between the ITC group of sulforaphane and the cysteine thiols of urease, leading to the loss of urease activity and subsequently mitigating the severity of Helicobacter pylori infection in the stomach. Furthermore, sulforaphane also exhibits significant inhibitory effects against other bacteria such as Pseudomonas aeruginosa and Campylobacter jejuni.

3.Anti-inflammatory Mechanism of Sulforaphane

An increasing number of studies have demonstrated the potent anti-inflammatory properties of sulforaphane. The NF-κB pathway, which encodes the transcription of numerous pro-inflammatory cytokines and chemokines, is a crucial target for sulforaphane in regulating inflammatory responses. In mammals, NF-κB family proteins typically exist as homodimers or heterodimers, with the p50/p65 heterodimer being the most common. When the signaling pathway is activated, IκB kinase (IKK) protein complexes phosphorylate IκB, leading to its degradation via the proteasome. This allows NF-κB to enter the nucleus and bind to specific DNA sequences, transcribing various inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-10 (IL-10). Studies have shown that sulforaphane inhibits the binding of NF-κB to nuclear DNA and the expression of its downstream genes through direct, reversible, and thiol-dependent modifications of NF-κB subunits or related co-factors, without affecting IκB degradation or NF-κB nuclear translocation.

Pre-treatment with sulforaphane during exposure to cardiopulmonary bypass (CPB) surgery can reduce the activation of p38 and NF-κB in circulating monocytes and inhibit the expression of inflammatory cytokines in circulating leukocytes. This suggests that sulforaphane can protect the kidneys from CPB-induced injury by inactivating inflammatory signaling pathways in leukocytes. Additionally, sulforaphane can also mitigate neuroinflammation by modulating the phenotype of immune cells, reducing the pro-inflammatory (M1) phenotype and increasing the anti-inflammatory (M2) phenotype.

Sulforaphane effectively alleviates dextran sulfate sodium-induced intestinal inflammation, as evidenced by reduced colonic symptoms such as altered stool formation and fecal bleeding. During intestinal inflammation, monocytes differentiate into specific immature macrophages upon activation by pathogen-associated molecular patterns. These macrophages then secrete pro-inflammatory cytokines, exacerbating the inflammatory response and barrier damage. Sulforaphane promotes the transition of macrophage phenotype from M1 to M2 via IL-10/signal transducer and activator of transcription 3 (STAT3) signaling, contributing to the resolution of the inflammatory state.

4.Anticancer Mechanism of Sulforaphane

Numerous studies have shown that sulforaphane can significantly reduce the incidence of various cancers, including lung, breast, bladder, prostate, and colon cancers, thereby improving human health. Sulforaphane exerts its anticancer effects by regulating pre-cancerous processes within cells, triggering apoptosis (programmed cell death), inducing cell cycle arrest, controlling angiogenesis in cancer cells, and effectively preventing and treating tumors.

During tumor development, sulforaphane can block the tumor cell cycle at the G1, S, or G2/M phases, induce apoptosis to initiate spontaneous programmed cell death in tumor cells, and stimulate autophagy to inhibit tumor progression. In the stage of tumor progression, sulforaphane inhibits angiogenesis, which is critical for the growth and metastasis of malignant tumors, thereby exerting a positive impact on preventing cancer cell dissemination. Overall, sulforaphane demonstrates a multifaceted approach in combating cancer by targeting various stages of tumor development and progression.

Furthermore, sulforaphane can prevent cancer development at its early stages by inhibiting the activity of phase I enzymes and inducing the production of phase II enzymes. In the first phase, sulforaphane inhibits the activation of precarcinogens. In the second phase, sulforaphane activates enzymes such as glutathione S-transferase (GST), UDP-glucuronosyl transferase (UGT), and quinone reductase (NQO1), which inhibit the expression of the oncogene CYP2E1, deactivate carcinogens, and thereby effectively prevent the occurrence of cancer. Studies have found that administering sulforaphane to female rats significantly reduces the activity of the potent carcinogen benzo[a]pyrene in their bodies, while also decreasing the activity of phase I enzymes and enhancing the activity of phase II enzymes, effectively preventing the development of lung cancer.

Additional studies have demonstrated that sulforaphane functions as a natural histone deacetylase inhibitor. It inhibits the transcription of histone deacetylase 5 (HDAC5) by downregulating upstream transcription factor 1 (USF1), leading to destabilization of lysine-specific demethylase 1 (LSD1) protein in breast cancer cells.

In investigations related to liver cancer cells, it has been discovered that sulforaphane significantly inhibits the proliferation of liver cancer cells by downregulating the expression of oncogenes such as CCND1, CCNB1, CDK1, CDK2, and CCNB1. Furthermore, sulforaphane inhibits the proliferation and angiogenesis of human liver cancer cell lines by stimulating the Nrf2 signaling cascade within these cells, thereby impeding their proliferation.

Studies have revealed that sulforaphane can significantly inhibit the proliferation of non-small cell lung cancer (NSCLC) cell lines H1299, 95C, and 95D. At low concentrations (1-5 μmol/L), it can prevent the migration and invasion of 95D and H1299 cells with relatively high metastatic potential. By altering histone modifications, sulforaphane reduces the level of miR-616-5p, resulting in the inactivation of the GSK3β/β-catenin signaling pathway. This subsequently inhibits epithelial-mesenchymal transition (EMT) and the metastasis of lung cancer cells.

References

[1] Sun Yiliang, Li Haiyan, Hong Hanjun, et al. Research Progress on the Physiological Functions of Sulforaphane from Cruciferous Plants and Its Application in Products [J]. Science and Technology of Food Industry, 2024, 45(02): 364-372.

[2] Zhao Songmin, Li Yingchang, Dong Gaoyuan, et al. Research Progress on the Functional Properties and Mechanisms of Sulforaphane [J]. Food and Fermentation Industries, 2023, 49(13): 357-362.

[3] Zhang Jingyi, Zheng Yan, Cui Fangchao, et al. Research Progress on the Synthesis, Functions, and Exogenous Regulation of Sulforaphane [J]. Journal of Food Safety and Quality, 2023, 14(12): 173-180.

About the Author

Xiaonisha, a food technology professional holding a Master's degree in Food Science, is currently employed at a prominent domestic pharmaceutical research and development company. Her primary focus lies in the development and research of nutritional foods, where she contributes her expertise and passion to create innovative products.