β-carotene isolated from the marine red alga, Gracillaria sp. potently attenuates the growth of human hepatocellular carcinoma (HepG2) cells by modulating multiple molecular pathways

Unraveling cancer progression pathways and phytochemical therapeutic strategies for its management

Cancer prevention is currently envisioned as a molecular-based approach to prevent carcinogenesis in pre-cancerous stages, i.e., dysplasia and carcinoma in situ. Cancer is the second-leading cause of mortality worldwide, and a more than 61% increase is expected by 2040. A detailed exploration of cancer progression pathways, including the NF-kβ signaling pathway, Wnt-B catenin signaling pathway, JAK-STAT pathway, TNF-α-mediated pathway, MAPK/mTOR pathway, and apoptotic and angiogenic pathways and effector molecules involved in cancer development, has been discussed in the manuscript. Critical evaluation of these effector molecules through molecular approaches using phytomolecules can intersect cancer formation and its metastasis. Manipulation of effector molecules like NF-kβ, SOCS, β-catenin, BAX, BAK, VEGF, STAT, Bcl2, p53, caspases, and CDKs has played an important role in inhibiting tumor growth and its spread. Plant-derived secondary metabolites obtained from natural sources have been extensively studied for their cancer-preventing potential in the last few decades. Eugenol, anethole, capsaicin, sanguinarine, EGCG, 6-gingerol, and resveratrol are some examples of such interesting lead molecules and are mentioned in the manuscript. This work is an attempt to put forward a comprehensive approach to understanding cancer progression pathways and their management using effector herbal molecules. The role of different plant metabolites and their chronic toxicity profiling in modulating cancer development pathways has also been highlighted.

Seaweeds and Their Secondary Metabolites: A Promising Drug Candidate With Novel Mechanisms Against Cancers and Tumor Angiogenesis

Cancer continually remains a severe threat to public health and requires constant demand for novel therapeutic drug candidates. Due to their multi-target orientation, lesser toxicity, and easy availability, natural compounds attract more attention from current scientific research interest than synthetic drug molecules. The plants and microorganisms produce a huge variety of secondary metabolites because of their physiological diversification, and the seaweeds occupy a prominent position as effective drug resources. Seaweeds comprise microscopic or macroscopic photosynthetic, multicellular, eukaryotic marine algae that commonly inhabit the coastal regions. Several molecules (such as polysaccharides, lipids, proteinaceous fractions, phenolic compounds, and alkaloids) are derived from seaweeds, and those small molecules are well attractive and more effective in cancer research programs. Their structural variation, derivative diversity, and quantity vary with seaweed species and geographical origin. Their smaller molecular weight, unique derivatives, hydrophobicity, and degree of sulfation are reported to be causes of their crucial role against different cancer cells in vitro. Several reports showed that those compounds selectively discriminate between normal and cancer cells based on receptor variations, enzyme deficiency, and structural properties. The present review aimed to give a concise explanation regarding their structural diversity, extractability, and mechanism of action related to their anti-cancer activities based on recently published data.

Ultrasound-based strategies for the recovery of microalgal carotenoids: Insights from green extraction methods to UV/MS-based identification

Carotenoids, versatile natural pigments with numerous health benefits, face environmental concerns associated with conventional petrochemical-based extraction methods and limitations of their synthetic equivalents. In this context, this study aims to introduce eco-friendly approaches using ultrasound-based strategies (probe and bath) for the extraction of carotenoids from microalgae, initially focusing on Microchloropsis gaditana and subsequently evaluating the versatility of the method by applying it to other microalgae species of interest (Tisochrysis lutea, Porphyridium cruentum, and Phaeodactylum tricornutum) and defatted microalgal residues. Among the approaches evaluated, the 5-min ultrasonic probe system with ethanol showed comparable carotenoid recovery efficiency to the reference method (agitation, 24 h, acetone) (9.4 ± 2.5 and 9.6 ± 3.2 mg g-1 carotenoids per dry biomass, for the green and the reference method, respectively). Moreover, the method's sustainability was demonstrated using the AGREEprep™ software (scored 0.62 out of 1), compared to the traditional method (0.22 out of 1). The developed method yielded high carotenoid contents across species with diverse cell wall compositions (3.1 ± 0.2, 2.1 ± 0.3, and 4.1 ± 0.1 mg g-1 carotenoid per dry biomass for T. lutea, P. cruentum, and P. tricornutum, respectively). Moreover, the application of the method to defatted biomass showed potential for microalgal valorization with carotenoid recovery rates of 41 %, 60 %, 61 %, and 100 % for M.gaditana, P. tricornutum, T. lutea, and P. cruentum, compared to the original biomass, respectively. Furthermore, by using high-performance liquid chromatography with a diode array detector (HPLC-DAD) and high-resolution mass spectrometry (HRMS), we reported the carotenoid and chlorophyll profiles of the different microalgae and evaluated the impact of the eco-friendly methods. The carotenoid and chlorophyll profiles varied depending on the species, biomass, and method used. In summary, this study advances a green extraction method with improved environmental sustainability and shorter extraction time, underscoring the potential of this approach as a valuable alternative for the extraction of microalgal pigments.

Comparing Pharmacological Potential of Freshwater Microalgae Carotenoids Towards Antioxidant and Anti-proliferative Activity on Liver Cancer (HUH7) Cell Line

Chemical-based carotenoids have large implications to health as they may cause adverse side effects. Naturally occurring carotenoids mainly from microalgal sources are emerging as excellent substitute to combat cancer diseases. Astaxanthin is the most powerful antioxidant that derived from selected established microalgae with limited yield. Microalgal bioprospecting may provide the high-yielding sources for astaxanthin production. Hence, in the present research, freshwater microalgae Monoraphidium sp. (NCM no. 5585) and Scenedesmus obliquus (NCM no. 5586) were chosen to explore the unique potential of producing astaxanthin. Identification of bioactive metabolites in extracted carotenoid was analyzed through HPLC. Astaxanthin is identified as a major bioactive metabolite in both carotenoid fraction and β carotene only in Scenedesmus obliquus. Antioxidant potential of microalgal carotenoids was obtained by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric-reducing antioxidant power (FRAP) assay. The anti-proliferation activity of the extracted carotenoid from Monoraphidium sp. and Scenedesmus obliquus was evaluated against hepatocellular liver carcinoma cell line HUH7 by 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay. Higher astaxanthin in Monoraphidium sp. leads to boosted antioxidant and anti-proliferation activity contrary to Scenedesmus obliquus that possess both astaxanthin and β carotene. Though freshwater microalgae have a huge potential to create beneficial metabolites like carotenoids, they are rarely studied in the pharmaceutical industry. This work was the first to investigate the anti-proliferative activity of Monoraphidium sp. and Scenedesmus obliquus carotenoid fraction on the HUH7 hepatocarcinoma cell line.

Global seaweed farming and processing in the past 20 years

Seaweed has emerged as one of the most promising resources due to its remarkable adaptability, short development period, and resource sustainability. It is an effective breakthrough to alleviate future resource crises. Algal resources have reached a high stage of growth in the past years due to the increased output and demand for seaweed worldwide. Several aspects global seaweed farming production and processing over the last 20 years are reviewed, such as the latest situation and approaches of seaweed farming. Research progress and production trend of various seaweed application are discussed. Besides, the challenges faced by seaweed farming and processing are also analyzed, and the related countermeasures are proposed, which can provide advice for seaweed farming and processing. The primary products, extraction and application, or waste utilization of seaweed would bring greater benefits with the continuous development and improvement of applications in various fields.

Graphical Abstract

Hyperglycaemia-induced human hepatocellular carcinoma (HepG2) cell proliferation through ROS-mediated P38 activation is effectively inhibited by a xanthophyll carotenoid, lutein

AIMS

Diabetic population have a twofold to threefold increased risk of developing liver cancer, and hyperglycaemia is a prime causative factor that propends the tumour cells to undergo aggressive metabolic growth. In this study, we aimed to examine the molecular mechanism by which lutein inhibits hyperglycaemia-induced human hepatocarcinoma (HepG2) cell proliferation.

METHODS

The effect of lutein on high glucose-induced proliferation was measured using the WST-1 reagent. Its effect on intracellular reactive oxygen species (ROS) levels was measured by DCF assay. The effect on the expression of antioxidant enzymes, cell cycle regulatory proteins and intracellular protein kinases was analysed by western blotting. The modulatory effect of lutein on different phases of the cell cycle was analysed by flow cytometry.

RESULTS

The data showed that lutein at 5 µM concentration significantly blocked glucose-promoted HepG2 cell proliferation. Suppression of high glucose-induced cell proliferation by lutein was not associated with apoptosis induction, but it was linked with inhibition of hyperglycaemia-mediated elevated ROS and upregulated expression of high glucose-mediated repressed heme oxygenase 1 (HO1). Furthermore, G2/M phase cell cycle arrest and associated phosphorylation of Cdk1 and P53 were found to be linked with suppressed hyperglycaemia-mediated cell proliferation by lutein. In addition, lutein inhibited hyperglycaemia-induced activation of P38 which relates to high glucose-induced ROS-mediated growth suppression and modulated the phosphorylation of Erk, JNK and Akt in hyperglycaemic HepG2 cells.

CONCLUSION

Our findings portray that sufficient intake of lutein may offer a negative impact on diabetes-associated tumour growth.

Neoxanthin prevents H2O2-induced cytotoxicity in HepG2 cells by activating endogenous antioxidant signals and suppressing apoptosis signals

BACKGROUND

The liver has a solid inbuilt antioxidant defense system to regulate oxidative stress. However, exposure to an excessive level of ROS causes liver injury. This study examined the cytoprotective effect of neoxanthin, a xanthophyll antioxidant molecule isolated from Solanum trilobatum in stress-induced HepG2 cells.

METHODS AND RESULTS

The cytotoxic effect of H₂O₂ and cytoprotective potential of β-carotene, lutein, and neoxanthin was analyzed by WST-1 assay. The intracellular ROS level and mitochondrial membrane potential (MMP) were measured using DCFH-DA (2', 7'-dichlorofluorescin diacetate) and JC-10 MMP assay. The expression of anti-oxidant and apoptotic markers was measured by western blot analysis. Neoxanthin pretreatment exhibited better protection than β-carotene and lutein against cell death caused by H₂O₂. It significantly arrested H₂O₂-mediated elevation of intracellular ROS levels and protected MMP. The intracellular antioxidant enzymes HO-1 and SOD-2 were upregulated by neoxanthin pretreatment. Neoxanthin also activated the protein expression of redox-sensitive transactivation factors, Nrf2 and NF-kB. The cytoprotective effect of neoxanthin was associated with increased expression of the anti-apoptotic protein, Bcl-2 and decreased pro-apoptotic protein Bax.

CONCLUSIONS

For the first time, our results demonstrate that neoxanthin offers adequate protection against stress-mediated cytotoxicity in hepatocytes by activating the intracellular antioxidant defense system and blocking apoptosis.

Role of BCL-2 Family Proteins in Apoptosis and its Regulation by Nutrients

In the body, millions of cells die and proliferate each day to maintain normal function and cooperation of all tissues, organs, and systems. Thus, programmed cell death, or apoptosis, is critical to sustain growth, development, and body health. The vital role of B-cell leukemia/lymphoma-2 (BCL-2) family proteins in apoptosis has been identified. The BCL-2 family includes both pro- and antiapoptotic proteins, which are structurally and functionally related, containing up to four BCL-2 homology (BH) motifs (BH1-4). There are also some nutritional factors that regulate apoptosis via the BCL-2 family proteins. In this review, the BCL-2 family proteins and their apoptosis-inducing mechanism have been discussed, along with the nutrient factors that regulate apoptosis through the BCL-2 family proteins.

Bioprospecting of Coralline Red Alga Amphiroa rigida J.V. Lamouroux: Volatiles, Fatty Acids and Pigments

Due to the lack of phytochemical composition data, the major goals of the present study on Amphiroa rigida J.V. Lamouroux were to: (a) investigate and compare volatilome profiles of fresh and air-dried samples obtained by headspace solid-phase microextraction (HS-SPME) and hydrodistillation (HD) followed by gas chromatography and mass spectrometry (GC/MS) analysis; (b) determine fatty acids profile by gas chromatography with flame ionization detector (GC-FID); (c) obtain the pigment profiles of semipurified extracts by high performance liquid chromatography (HPLC) and (d) evaluate the antioxidant and antimicrobial activities of its less polar fractions. The comparison of headspace of fresh (FrAr) and air-dried (DrAr) samples revealed many similarities regarding the presence and abundance of the major (heptadecane and pentadecane) and minor compounds. The hydrodistillate (HD) of DrAr profile was quite different in comparison to HD-FrAr. The predominant compound in HD-FrAr was (E)-phytol. In HD-DrAr, its percentage was approximately one-half reduced, but the abundance of its degradation product phytone and of unsaturated and oxygenated compounds increased indicating more intense fatty acid decomposition and oxidation during drying. The fatty acid determination revealed that the most dominant was palmitic acid (42.86%) followed by eicosapentaenoic acid (19.14%) and stearic acid (11.65%). Among the pigments, A. rigida contained fucoxanthin (0.63 mg g⁻¹ of dry fraction), lutein (5.83 mg g⁻¹), β-carotene (6.18 mg g⁻¹) and chlorophyll a (13.65 mg g⁻¹). The analyzed less polar fractions of A. rigida exhibited antioxidant scavenging activity with diammonium salt of 2,2′-azino-bis (3-ethylbenzthiazolin-6-yl) sulfonic acid (ABTS) assay up to 3.87 mg g⁻¹ trolox equivalents (TE), and with the oxygen radical absorbance capacity (ORAC) assay up to 825.63 μmol g⁻¹ TE (with carotenoids as the major contributors).

Inhibitory efficacy of lutein on adipogenesis is associated with blockage of early phase regulators of adipocyte differentiation

A comprehensive molecular mechanistic role of lutein on adipogenesis is not well understood. The present study focused to evaluate the effect of lutein at the early and late phase of adipocyte differentiation in vitro using a 3T3-L1 cell model. The effect of purified carotenoid on the viability of normal and differentiated 3T3-L1 cells was analyzed by WST-1 assay. Oil Red O and Nile red staining were employed to observe lipid droplets in mature adipocytes. The effect of lutein on gene and protein expression of major transcription factors and adipogenic markers was analyzed by RT-PCR and western blotting, respectively. The role of lutein on mitotic clonal expansion was analyzed by flow cytometry. The results showed a significant reduction (p < 0.05) in the accumulation of lipid droplets in lutein-treated (5 μM) cells. Inhibition in lipid accumulation was associated with down-regulated expression of CEBP-α and PPAR-γ at gene and protein levels. Subsequently, lutein repressed gene expression of FAS, FABP4, and SCD1 in mature adipocytes. Interestingly, it blocks the protein expression of CEBP-α and PPAR-γ in the initial stages of adipocyte differentiation. This early-stage inhibition of adipocyte differentiation is linked with repressed phosphorylation AKT and ERK. Further, upregulated cyclin D and down-regulated CDK4 and CDK2 in lutein treated adipocytes enumerate its role in delaying the cell cycle progression at the G0/G1 phase. Our results emphasize that adipogenesis inhibitory efficacy of lutein is potentiated by halting early phase regulators of adipocyte differentiation, which strengthens the competency of lutein besides its inevitable presence in the human body.

Lutein inhibits breast cancer cell growth by suppressing antioxidant and cell survival signals and induces apoptosis

Reduced risk of breast cancer upon intake of lutein-rich food supplements creates an interest to investigate the molecular mechanism underlying the growth inhibitory potential of lutein in MCF-7 and MDA-MB-231 cells. Lutein purified from Spinacia oleracea was identified by high-performance liquid chromatography and liquid chromatography-mass spectrometry. The cell viability was measured by water-soluble tetrazolium-1 assay. The intracellular reactive oxygen species level was examined by 2',7'-dichlorofluorescein assay. The protein expression of the markers of antioxidant defense, cell survival, and apoptosis was analyzed by western blot analysis. The induction of apoptosis by lutein was measured by 4',6-diamidino-2-phenylindole staining and caspase-3 activity assay. The purified lutein inhibited the viability of MCF-7 and MDA-MB-231 cells. The growth inhibitory effect of lutein was associated with suppressed protein expression of superoxide dismutase-2 and heme oxygenase-1, and its transcription factor nuclear factor erythroid 2-related factor-2. Lutein treatment subsequently blocked the expression of intracellular cell survival proteins, phosphorylated protein kinase B, phosphorylated extracellular-regulated kinase 1/2, and nuclear factor-kB. Suppression of antioxidant defense and cell survival markers by lutein was further linked to apoptosis induction with elevated caspase-3 activity and downregulated expression of Bcl-2 and poly-ADP ribose polymerase. Our results emphasize a significant role of lutein as an effective inhibitor of human breast cancer cell growth that activates cell death partly through the modulation of antioxidant defense response-linked cell survival signaling markers.

Pro-Oxidant Actions of Carotenoids in Triggering Apoptosis of Cancer Cells: A Review of Emerging Evidence

Carotenoids are well known for their potent antioxidant function in the cellular system. However, in cancer cells with an innately high level of intracellular reactive oxygen species (ROS), carotenoids may act as potent pro-oxidant molecules and trigger ROS-mediated apoptosis. In recent years, the pro-oxidant function of several common dietary carotenoids, including astaxanthin, β-carotene, fucoxanthin, and lycopene, has been investigated for their effective killing effects on various cancer cell lines. Besides, when carotenoids are delivered with ROS-inducing cytotoxic drugs (e.g., anthracyclines), they can minimize the adverse effects of these drugs on normal cells by acting as antioxidants without interfering with their cytotoxic effects on cancer cells as pro-oxidants. These dynamic actions of carotenoids can optimize oxidative stress in normal cells while enhancing oxidative stress in cancer cells. This review discusses possible mechanisms of carotenoid-triggered ROS production in cancer cells, the activation of pro-apoptotic signaling by ROS, and apoptotic cell death. Moreover, synergistic actions of carotenoids with ROS-inducing anti-cancer drugs are discussed, and research gaps are suggested.

Lutein reverses hyperglycemia-mediated blockage of Nrf2 translocation by modulating the activation of intracellular protein kinases in retinal pigment epithelial (ARPE-19) cells

Diabetic retinopathy (DR) is a major cause of acquired blindness among working adults. The retinal pigment epithelium (RPE), constitutes an outer blood-retinal barrier, is vastly affected in diabetic humans and animals. Lower levels of lutein in the serum and retina of diabetic population, and beneficial effects of carotenoids supplementation in diabetic retinopathy patients created an interest to examine the protective effect of lutein on hyperglycemia-mediated changes in oxidative stress and antioxidant defense system in ARPE-19 cells. The WST-1 assay was performed to analyze the impact of glucose, and lutein on the viability of ARPE-19. The intracellular oxidative stress was measured by a DCF (dichlorofluorescein) assay, mitochondrial membrane potential (MMP) was monitored using a JC-10 MMP assay kit and GSH level was examined using GSH/GSSG ratio detection kit. The oxidative stress markers, protein carbonyl and malondialdehyde were spectrophotometrically measured using 2,4-dinitrophenylhydrazine and 2-thiobarbituric acid, respectively. The expression of endogenous antioxidant enzymes and regulatory proteins in ARPE-19 was quantified by western blotting. The localization of Nrf2 protein was examined by immunofluorescent staining. The results show that lutein (up to 1.0 μM) did not affect the viability of ARPE-19 grown in both normal and high-glucose conditions. Lutein treatment blocked high glucose-mediated elevation of intracellular ROS, protein carbonyl and malondialdehyde content in ARPE-19 cells. The decreased MMP and GSH levels observed in ARPE-19 grown under high-glucose condition were rescued by lutein treatment. Further, lutein protected high glucose-mediated down-regulation of a redox-sensitive transcription factor, Nrf2, and antioxidant enzymes, SOD2, HO-1, and catalase. This protective effect of lutein was linked with activated nuclear translocation of Nrf2, which was associated with increased activation of regulatory proteins such as Erk and AKT. Our study indicates that improving the concentration of lutein in the retina could protect RPE from diabetes-associated damage.