The Flaxseed-Derived Lignan Phenolic Secoisolariciresinol Diglucoside (SDG) Protects Non-Malignant Lung Cells from Radiation Damage

Polyphenols as Potential Protectors against Radiation-Induced Adverse Effects in Patients with Thoracic Cancer

Radiotherapy is one of the standard treatment approaches used against thoracic cancers, occasionally combined with chemotherapy, immunotherapy and molecular targeted therapy. However, these cancers are often not highly sensitive to standard of care treatments, making the use of high dose radiotherapy necessary, which is linked with high rates of radiation-induced adverse effects in healthy tissues of the thorax. These tissues remain therefore dose-limiting factors in radiation oncology despite recent technological advances in treatment planning and delivery of irradiation. Polyphenols are metabolites found in plants that have been suggested to improve the therapeutic window by sensitizing the tumor to radiotherapy, while simultaneously protecting normal cells from therapy-induced damage by preventing DNA damage, as well as having anti-oxidant, anti-inflammatory or immunomodulatory properties. This review focuses on the radioprotective effect of polyphenols and the molecular mechanisms underlying these effects in the normal tissue, especially in the lung, heart and esophagus.

Anticancer potential of flaxseed lignans, their metabolites and synthetic counterparts in relation with molecular targets: current challenges and future perspectives

Lignans are known dietary polyphenols found in cereals, plants and seeds. Flaxseed is one of the major sources of lignans mainly existing in the form of secoisolariciresinol diglucoside (SDG) which can be metabolised by the gut microbes into secoisolariciresinol (SECO) and mammalian lignan (enterodiol and enterolactone) that are easily absorbed through the intestines. Numerous studies reveal that flaxseed lignans (FLs) can be promising chemotherapeutics/chemopreventive agents. Their anticancer activity can occur through the induction of apoptosis, inhibition of cell proliferation, and the hindering of metastasis and angiogenesis. The anti-carcinogenesis of flaxseed lignans is achieved through multiple molecular mechanisms involving biochemical entities such as cellular kinases, cell cycle mediators, transcription factors, inflammatory cytokines, reactive oxygen species, and drug transporters. This review summarizes the bioavailability of FLs, their anticancer mechanisms in relevance to molecular targets, safety, and the scope of future research. Overall, FLs can be utilized in functional foods, dietary supplements, and pharmaceuticals for the management and prevention of cancers.

Distribution, biosynthesis and therapeutic potential of lignans

Lignans have long been known for their abundant therapeutic properties due to their polyphenolic structure. Linseed is the richest plant source of lignans and has been studied widely for their properties. The most prevalent lignan, secoisolariciresinol diglucoside (SDG), is consumed with linseed and converted into mammalian lignans, enterodiol (END) and enterolactone (ENL), by the gut microbiota. SDG can easily be assessed using HPLC and its deglycosylated form viz secoisolariciresinol can be asses using GC-MS techniques. Variety of extraction and analysis methods has been reported for plant lignans. SDG is known to have therapeutic properties including anti-oxidant, anti-cancerous, anti-inflammatory, modulation of gene expression, anti-diabetic, estrogenic and anti-estrogenic. Despite a large number of bioactivities, strong evidences for the underlying mechanisms for most of the properties are still unknown. SDG is most studied for its anti-cancerous properties. But the use of lignans as anti-carcinogenic agent is limited and commercially not reported due to challenges of purification at commercial level, rapid metabolism, untargeted delivery and toxic compounds associated with lignans. Exploration of more prominent and active derivatives of SDG and their targeted drug delivery should be an important research toward the use of bioactive lignans of linseed.

Synthetic Secoisolariciresinol Diglucoside (LGM2605) Prevents Asbestos-Induced Inflammation and Genotoxic Cell Damage in Human Mesothelial Cells

Although alveolar macrophages play a critical role in malignant transformation of mesothelial cells following asbestos exposure, inflammatory and oxidative processes continue to occur in the mesothelial cells lining the pleura that may contribute to the carcinogenic process. Malignant transformation of mesothelial cells following asbestos exposure occurs over several decades; however, amelioration of DNA damage, inflammation, and cell injury may impede the carcinogenic process. We have shown in an in vitro model of asbestos-induced macrophage activation that synthetic secoisolariciresinol diglucoside (LGM2605), given preventively, reduced inflammatory cascades and oxidative/nitrosative cell damage. Therefore, it was hypothesized that LGM2605 could also be effective in reducing asbestos-induced activation and the damage of pleural mesothelial cells. LGM2605 treatment (50 µM) of huma n pleural mesothelial cells was initiated 4 h prior to exposure to asbestos (crocidolite, 20 µg/cm2). Supernatant and cells were evaluated at 0, 2, 4, and 8 h post asbestos exposure for reactive oxygen species (ROS) generation, DNA damage (oxidized guanine), inflammasome activation (caspase-1 activity) and associated pro-inflammatory cytokine release (IL-1β, IL-18, IL-6, TNFα, and HMGB1), and markers of oxidative stress (malondialdehyde (MDA) and 8-iso-prostaglandin F2a (8-iso-PGF2α). Asbestos induced a time-dependent ROS increase that was significantly (p < 0.0001) reduced (29.4%) by LGM2605 treatment. LGM2605 pretreatment also reduced levels of asbestos-induced DNA damage by 73.6% ± 1.0%. Although levels of inflammasome-activated cytokines, IL-1β and IL-18, reached 29.2 pg/mL ± 0.7 pg/mL and 43.9 pg/mL ± 0.8 pg/mL, respectively, LGM2605 treatment significantly (p < 0.0001) reduced cytokine levels comparable to baseline (non-asbestos exposed) values (3.8 pg/mL ± 0.2 pg/mL and 5.4 pg/mL ± 0.2 pg/mL, respectively). Furthermore, levels of IL-6 and TNFα in asbestos-exposed mesothelial cells were high (289.1 pg/mL ± 2.9 pg/mL and 511.3 pg/mL ± 10.2 pg/mL, respectively), while remaining undetectable with LGM2605 pretreatment. HMGB1 (a key inflammatory mediator and initiator of malignant transformation) release was reduced 75.3% ± 0.4% by LGM2605. Levels of MDA and 8-iso-PGF2α, markers of oxidative cell injury, were significantly (p < 0.001) reduced by 80.5% ± 0.1% and 76.6% ± 0.3%, respectively. LGM2605, given preventively, reduced ROS generation, DNA damage, and inflammasome-activated cytokine release and key inflammatory mediators implicated in asbestos-induced malignant transformation of normal mesothelial cells.

The Impact of Heat Treatment of Quercetin and Myricetin on their Activities to Alleviate the Acrylamide-Induced Cytotoxicity and Barrier Loss in IEC-6 Cells

Two flavonols quercetin and myricetin were assessed for their in vitro activities to attenuate the acrylamide-induced cytotoxicity and barrier loss in rat intestinal epithelial (IEC-6) cells and to identify whether heat treatment of the flavonols might cause activity changes. The results showed that the flavonols could alleviate the acrylamide-caused cell injury, resulting in higher cell viability, lower lactate dehydrogenase release, and less formation of reactive oxygen species. Meanwhile, the flavonols could antagonize the acrylamide-induced barrier dysfunction via decreasing the paracellular permeability, increasing the transepithelial resistance of cell monolayer, and enhancing the expression of three tight junction proteins namely occludin, claudin-1, and zonula occludens-1. The flavonols also could down-regulate the expression of JNK/Src proteins and thus cause lower relative protein ratios of p-JNK/JNK and p-Src/Src, resulting in a suppressed JNK/Src activation. Totally, quercetin was more potent than myricetin to exert these assessed activities, while the heated flavonols obtained lower activity than the unheated ones. It is thus concluded that the flavonols had beneficial activities towards the intestinal epithelial cells with acrylamide exposure by alleviating the acrylamide-induced cytotoxicity and barrier disruption, while heat treatment of the flavonols was unfavorable because it led to a reduced flavonol activity to the cells.

Late Inflammation Induced by Asbestiform Fibers in Mice Is Ameliorated by a Small Molecule Synthetic Lignan

Exposure to Libby amphibole (LA) asbestos-like fibers is associated with increased risk of asbestosis, mesothelioma, pulmonary disease, and systemic autoimmune disease. LGM2605 is a small molecule antioxidant and free radical scavenger, with anti-inflammatory effects in various disease models. The current study aimed to determine whether the protective effects of LGM2605 persist during the late inflammatory phase post-LA exposure. Male and female C57BL/6 mice were administered daily LGM2605 (100 mg/kg) via gel cups for 3 days before and 14 days after a 200 µg LA given via intraperitoneal (i.p.) injection. Control mice were given unsupplemented gel cups and an equivalent dose of i.p. saline. On day 14 post-LA treatment, peritoneal lavage was assessed for immune cell influx, cytokine concentrations, oxidative stress biomarkers, and immunoglobulins. During the late inflammatory phase post-LA exposure, we noted an alteration in trafficking of both innate and adaptive immune cells, increased pro-inflammatory cytokine concentrations, induction of immunoglobulin isotype switching, and increased oxidized guanine species. LGM2605 countered these changes similarly among male and female mice, ameliorating late inflammation and altering immune responses in late post-LA exposure. These data support possible efficacy of LGM2605 in the prolonged treatment of LA-associated disease and other inflammatory conditions.

Copper Oxide Nanoparticle-Induced Acute Inflammatory Response and Injury in Murine Lung Is Ameliorated by Synthetic Secoisolariciresinol Diglucoside (LGM2605)

Metal-oxide nanoparticles (MO-NPs), such as the highly bioreactive copper-based nanoparticles (CuO-NPs), are widely used in manufacturing of hundreds of commercial products. Epidemiological studies correlated levels of nanoparticles in ambient air with a significant increase in lung disease. CuO-NPs, specifically, were among the most potent in a set of metal-oxides and carbons studied in parallel regarding DNA damage and cytotoxicity. Despite advances in nanotoxicology research and the characterization of their toxicity, the exact mechanism(s) of toxicity are yet to be defined. We identified chlorination toxicity as a damaging consequence of inflammation and myeloperoxidase (MPO) activation, resulting in macromolecular damage and cell damage/death. We hypothesized that the inhalation of CuO-NPs elicits an inflammatory response resulting in chlorination damage in cells and lung tissues. We further tested the protective action of LGM2605, a synthetic small molecule with known scavenging properties for reactive oxygen species (ROS), but most importantly, for active chlorine species (ACS) and an inhibitor of MPO. CuO-NPs (15 µg/bolus) were instilled intranasally in mice and the kinetics of the inflammatory response in lungs was evaluated 1, 3, and 7 days later. Evaluation of the protective action of LGM2605 was performed at 24 h post-challenge, which was selected as the peak acute inflammatory response to CuO-NP. LGM2605 was given daily via gavage to mice starting 2 days prior to the time of the insult (100 mg/kg). CuO-NPs induced a significant inflammatory influx, inflammasome-relevant cytokine release, and chlorination damage in mouse lungs, which was mitigated by the action of LGM2605. Preventive action of LGM2605 ameliorated the adverse effects of CuO-NP in lung.

Assessment of a Small Molecule Synthetic Lignan in Enhancing Oxidative Balance and Decreasing Lipid Accumulation in Human Retinal Pigment Epithelia

Visual function depends on the intimate structural, functional and metabolic interactions between the retinal pigment epithelium (RPE) and the neural retina. The daily phagocytosis of the photoreceptor outer segment tips by the overlaying RPE provides essential nutrients for the RPE itself and photoreceptors through intricate metabolic synergy. Age-related retinal changes are often characterized by metabolic dysregulation contributing to increased lipid accumulation and peroxidation as well as the release of proinflammatory cytokines. LGM2605 is a synthetic lignan secoisolariciresinol diglucoside (SDG) with free radical scavenging, antioxidant and anti-inflammatory properties demonstrated in diverse in vitro and in vivo inflammatory disease models. In these studies, we tested the hypothesis that LGM2605 may be an attractive small-scale therapeutic that protects RPE against inflammation and restores its metabolic capacity under lipid overload. Using an in vitro model in which loss of the autophagy protein, LC3B, results in defective phagosome degradation and metabolic dysregulation, we show that lipid overload results in increased gasdermin cleavage, IL-1 β release, lipid accumulation and decreased oxidative capacity. The addition of LGM2605 resulted in enhanced mitochondrial capacity, decreased lipid accumulation and amelioration of IL-1 β release in a model of defective lipid homeostasis. Collectively, these studies suggest that lipid overload decreases mitochondrial function and increases the inflammatory response, with LGM2605 acting as a protective agent.

Short-term exposure to synthetic flaxseed lignan LGM2605 alters gut microbiota in mice

LGM2605 is a synthetic version of the naturally occurring flaxseed lignan secoisolariciresinol diglucoside (SDG), with known anti‐inflammatory and antioxidant properties; however, its effects on gut microbial composition have not previously been evaluated. In the present study, we sought to determine how the 10‐day oral administration of LGM2605 alters the gut microbiota of mice. Eight‐week‐old female C57BL/6 mice were treated with either LGM2605 or saline, administered daily via oral gavage over a 10‐day treatment period. Upon termination of treatment, mouse cecums (n = 31) were collected, and cecal DNA was isolated. 16S rRNA genes were sequenced and analyzed in Mothur to identify changes in gut microbial composition induced by LGM2605 treatment (v. saline control). We then assessed community composition, performed indicator taxa analysis, and measured alpha and beta diversity. Overall, LGM2605 significantly altered the gut microbiota of mice; we reported alterations in 3 bacterial phyla and 22 genera as a result of treatment. The study here identifies for the first time significant alterations in the gut microbiota of mice following oral administration of LGM2605, in general shifting toward a more anti‐inflammatory composition. These findings lay the foundation for future investigations utilizing LGM2605 to control gut dysbiosis and, by extension, systemic inflammation.

Synthetic Secoisolariciresinol Diglucoside Attenuates Established Pain, Oxidative Stress and Neuroinflammation in a Rodent Model of Painful Radiculopathy

Painful cervical radiculopathy is characterized by chronic neuroinflammation that lowers endogenous antioxidant responses leading to the development of oxidative stress and pain after neural trauma. Therefore, antioxidants such as secoisolariciresinol diglucoside (SDG), that promote antioxidant signaling and reduce oxidative damage may also provide pain relief. This study investigated if repeated systemic administration of synthetic SDG after a painful root compression reduces the established pain, oxidative stress and spinal glial activation that are typically evident. SDG was administered on days 1-3 after compression and the extent of oxidative damage in the dorsal root ganglia (DRG) and spinal cord was measured at day 7 using the oxidative stress markers 8-hydroxguanosine (8-OHG) and nitrotyrosine. Spinal microglial and astrocytic activation were also separately evaluated at day 7 after compression. In addition to reducing pain, SDG treatment reduced both spinal 8-OHG and nitrotyrosine, as well as peripheral 8-OHG in the DRG. Moreover, SDG selectively reduced glial activation by decreasing the extent of astrocytic but not microglial activation. These findings suggest that synthetic SDG may attenuate existing radicular pain by suppressing the oxidative stress and astrocytic activation that develop after painful injury, possibly identifying it as a potent therapeutic for painful radiculopathies.

Lignans from linseed (Linum usitatissimum L.) and its allied species: Retrospect, introspect and prospect

Lignans are complex diphenolic compounds representing phytoestrogens and occur widely across the plant kingdom. Formed by the coupling of two coniferyl alcohol residues, lignans constitute major plant "specialized metabolites" with exceptional biological attributes that aid in plant defence and provide health benefits in humans by reducing the risk of ailments such as cancer, diabetes etc. Linseed (Linum usitatissimum L.) is one of the richest sources of lignans followed by cereals and legumes. Among the various types of lignans, secoisolariciresinol diglucoside (SDG) is considered as the essential and nutrient rich lignan in linseed. Lignans exhibit established antimitotic, antiviral and anti-tumor properties that contribute to their medicinal value. The present review seeks to provide a holistic view of research in the past and present times revolving around lignans from linseed and its allied species. This review attempts to elucidate sources, structures and functional properties of lignans, along with detailed biosynthetic mechanisms operating in plants. It summarizes various methods for the determination of lignan content in plants. Biotechnological interventions (in planta and in vitro) aimed at enriching lignan content and adoption of integrative approaches that might further enhance lignan content and medicinal and nutraceutical value of Linum spp. have also been discussed.

Randomized Phase IIB Trial of the Lignan Secoisolariciresinol Diglucoside in Premenopausal Women at Increased Risk for Development of Breast Cancer

We conducted a multiinstitutional, placebo-controlled phase IIB trial of the lignan secoisolariciresinol diglucoside (SDG) found in flaxseed. Benign breast tissue was acquired by random periareolar fine needle aspiration (RPFNA) from premenopausal women at increased risk for breast cancer. Those with hyperplasia and ≥2% Ki-67 positive cells were eligible for randomization 2:1 to 50 mg SDG/day (Brevail) versus placebo for 12 months with repeat bio-specimen acquisition. The primary endpoint was difference in change in Ki-67 between randomization groups. A total of 180 women were randomized, with 152 ultimately evaluable for the primary endpoint. Median baseline Ki-67 was 4.1% with no difference between arms. Median Ki-67 change was -1.8% in the SDG arm (P = 0.001) and -1.2% for placebo (P = 0.034); with no significant difference between arms. As menstrual cycle phase affects proliferation, secondary analysis was performed for 117 women who by progesterone levels were in the same phase of the menstrual cycle at baseline and off-study tissue sampling. The significant Ki-67 decrease persisted for SDG (median = -2.2%; P = 0.002) but not placebo (median = -1.0%). qRT-PCR was performed on 77 pairs of tissue specimens. Twenty-two had significant ERα gene expression changes (<0.5 or >2.0) with 7 of 10 increases in placebo and 10 of 12 decreases for SDG (P = 0.028), and a difference between arms (P = 0.017). Adverse event incidence was similar in both groups, with no evidence that 50 mg/day SDG is harmful. Although the proliferation biomarker analysis showed no difference between the treatment group and the placebo, the trial demonstrated use of SDG is tolerable and safe.

In silico and in vitro identification of secoisolariciresinol as a re-sensitizer of P-glycoprotein-dependent doxorubicin-resistance NCI/ADR-RES cancer cells

P-glycoprotein (P-gp) is one of the highly expressed cancer cell efflux transporters that cause the failure of chemotherapy. To reverse P-gp induced multidrug resistance, we employed a flaxseed-derived lignan; secoisolariciresinol (SECO) that acts as an inhibitor of breast cancer resistance protein; another efflux transporter that shares some substrate/inhibitor specificity with P-gp. Molecular dynamics (MD) simulation identified SECO as a possible P-gp inhibitor. Comparing root mean square deviation (RMSD) of P-gp bound with SECO with that bound to its standard inhibitor verapamil showed that fluctuations in RMSD were lower in P-gp bound to SECO demonstrating higher stability of the complex of P-gp with SECO. In addition, the superimposition of P-gp structures after MD simulation showed that the nucleotide-binding domains of P-gp bound to SECO undertook a more central closer position compared with that bound to verapamil. Using rhodamine efflux assay on NCI/ADR-RES cancer cells, SECO was confirmed as a P-gp inhibitor, where cells treated with 25 or 50 µM of SECO showed significantly higher fluorescence intensity compared to control. Using MTT assay, SECO alone showed dose-dependent cytotoxicity, where 25 or 50 µM of SECO caused significantly less NCI/ADR-RES cellular viability compared to control. Furthermore, when 50 µM of SECO was added to doxorubicin (DOX), an anticancer drug, SECO significantly enhanced DOX-induced cytotoxicity compared to DOX alone. The combination index calculated by CompuSyn software indicated synergism between DOX and SECO. Our results suggest SECO as a novel P-gp inhibitor that can re-sensitize cancer cells during DOX chemotherapy.

Ozone-induced enhancement of airway hyperreactivity in rhesus macaques: Effects of antioxidant treatment

BACKGROUND

Ozone (O3) inhalation elicits airway inflammation and impairs treatment responsiveness in asthmatic patients. The underlying immune mechanisms have been difficult to study because of the lack of relevant experimental models. Rhesus macaques spontaneously have asthma and have a similar immune system to human subjects.

OBJECTIVES

We sought to investigate mucosal immune changes after O3 inhalation in a clinically relevant nonhuman primate asthma model and to study the effects of an antioxidant synthetic lignan (synthetic secoisolariciresinol diglucoside [LGM2605]).

METHODS

A cohort of macaques (n = 17) previously characterized with airway hyperreactivity (AHR) to methacholine was assessed (day 1). Macaques were treated (orally) with LGM2605 (25 mg/kg) or placebo twice per day for 7 days, exposed to 0.3 ppm O3 or air for 6 hours (on day 7), and studied 12 hours later (day 8). Lung function, blood and bronchoalveolar lavage (BAL) fluid immune cell profile, and bronchial brushing and blood cell mRNA expression were assessed.

RESULTS

O3 induced significant BAL fluid neutrophilia and eosinophilia and increased AHR and expression of IL6 and IL25 mRNA in the airway epithelium together with increased BAL fluid group 2 innate lymphoid cell (ILC2s), CD1c+ myeloid dendritic cell, and CD4+ T-cell counts and diminished surfactant protein D expression. Although LGM2605 attenuated some of the immune and inflammatory changes, it completely abolished O3-induced AHR.

CONCLUSION

ILC2s, CD1c+ myeloid dendritic cells, and CD4+ T cells are selectively involved in O3-induced asthma exacerbation. The inflammatory changes were partially prevented by antioxidant pretreatment with LGM2605, which had an unexpectedly disproportionate protective effect on AHR.

Seeds

A wide variety of plant species provide edible seeds. Seeds are the dominant source of human calories and protein. The most important and popular seed food sources are cereals, followed by legumes and nuts. Their nutritional content of fiber, protein, and monounsaturated/polyunsaturated fats make them extremely nutritious. They are important additions to our daily food consumption. When consumed as part of a healthy diet, seeds can help reduce blood sugar, cholesterol, and blood pressure.

Flaxseed Lignans as Important Dietary Polyphenols for Cancer Prevention and Treatment: Chemistry, Pharmacokinetics, and Molecular Targets

Cancer causes considerable morbidity and mortality across the world. Socioeconomic, environmental, and lifestyle factors contribute to the increasing cancer prevalence, bespeaking a need for effective prevention and treatment strategies. Phytochemicals like plant polyphenols are generally considered to have anticancer, anti-inflammatory, antiviral, antimicrobial, and immunomodulatory effects, which explain their promotion for human health. The past several decades have contributed to a growing evidence base in the literature that demonstrate ability of polyphenols to modulate multiple targets of carcinogenesis linking models of cancer characteristics (i.e., hallmarks and nutraceutical-based targeting of cancer) via direct or indirect interaction or modulation of cellular and molecular targets. This evidence is particularly relevant for the lignans, an ubiquitous, important class of dietary polyphenols present in high levels in food sources such as flaxseed. Literature evidence on lignans suggests potential benefit in cancer prevention and treatment. This review summarizes the relevant chemical and pharmacokinetic properties of dietary polyphenols and specifically focuses on the biological targets of flaxseed lignans. The consolidation of the considerable body of data on the diverse targets of the lignans will aid continued research into their potential for use in combination with other cancer chemotherapies, utilizing flaxseed lignan-enriched natural products.

Chemically synthesized Secoisolariciresinol diglucoside (LGM2605) improves mitochondrial function in cardiac myocytes and alleviates septic cardiomyopathy

Sepsis is the overwhelming systemic immune response to infection, which can result in multiple organ dysfunction and septic shock. Myocardial dysfunction during sepsis is associated with advanced disease and significantly increased in-hospital mortality. Our group has shown that energetic failure and excess reactive oxygen species (ROS) generation constitute major components of myocardial dysfunction in sepsis. Because ROS production is central to cellular metabolic health, we tested if the synthetic anti-oxidant lignan secoisolariciresinol diglucoside (SDG; LGM2605) would alleviate septic cardiac dysfunction and investigated the underlying mechanism. Using the cecal ligation and puncture (CLP) mouse model of peritonitis-induced sepsis, we observed impairment of cardiac function beginning at 4 h post-CLP surgery. Treatment of mice with LGM2605 (100 mg/kg body weight, i.p.) 6 h post-CLP surgery reduced cardiac ROS accumulation and restored cardiac function. Assessment of mitochondrial respiration (Seahorse XF) in primary cardiomyocytes obtained from adult C57BL/6 mice that had undergone CLP and treatment with LGM2605 showed restored basal and maximal respiration, as well as preserved oxygen consumption rate (OCR) associated with spare capacity. Further analyses aiming to identify the cellular mechanisms that may account for improved cardiac function showed that LGM2605 restored mitochondria abundance, increased mitochondrial calcium uptake and preserved mitochondrial membrane potential. In addition to protecting against cardiac dysfunction, daily treatment with LGM2605 and antibiotic ertapenem (70 mg/kg) protected against CLP-associated mortality and reversed hypothermia when compared against mice receiving ertapenem and saline. Therefore, treatment of septic mice with LGM2605 emerges as a novel pharmacological approach that reduces cardiac ROS accumulation, protects cardiac mitochondrial function, alleviates cardiac dysfunction, and improves survival.

LGM2605 Reduces Space Radiation-Induced NLRP3 Inflammasome Activation and Damage in In Vitro Lung Vascular Networks

Updated measurements of charged particle fluxes during the transit from Earth to Mars as well as on site measurements by Curiosity of Martian surface radiation fluxes identified potential health hazards associated with radiation exposure for human space missions. Designing mitigation strategies of radiation risks to astronauts is critical. We investigated radiation-induced endothelial cell damage and its mitigation by LGM2605, a radioprotector with antioxidant and free radical scavenging properties. We used an in vitro model of lung vascular networks (flow-adapted endothelial cells; FAECs), exposed to gamma rays, low/higher linear energy transfer (LET) protons (3⁻4 or 8⁻10 keV/µm, respectively), and mixed field radiation sources (gamma and protons), given at mission-relevant doses (0.25 gray (Gy)⁻1 Gy). We evaluated endothelial inflammatory phenotype, NLRP3 inflammasome activation, and oxidative cell injury. LGM2605 (100 µM) was added 30 min post radiation exposure and gene expression changes evaluated 24 h later. Radiation induced a robust increase in mRNA levels of antioxidant enzymes post 0.25 Gy and 0.5 Gy gamma radiation, which was significantly decreased by LGM2605. Intercellular cell adhesion molecule-1 (ICAM-1) and NOD-like receptor protein 3 (NLRP3) induction by individual or mixed-field exposures were also significantly blunted by LGM2605. We conclude that LGM2605 is a likely candidate to reduce tissue damage from space-relevant radiation exposure.

Synthetic Lignan Secoisolariciresinol Diglucoside (LGM2605) Reduces Asbestos-Induced Cytotoxicity in an Nrf2-Dependent and -Independent Manner

Asbestos exposure triggers inflammatory processes associated with oxidative stress and tissue damage linked to malignancy. LGM2605 is the synthetic lignan secoisolariciresinol diglucoside (SDG) with free radical scavenging, antioxidant, and anti-inflammatory properties in diverse inflammatory cell and mouse models, including exposure to asbestos fibers. Nuclear factor-E2 related factor 2 (Nrf2) activation and boosting of endogenous tissue defenses were associated with the protective action of LGM2605 from asbestos-induced cellular damage. To elucidate the role of Nrf2 induction by LGM2605 in protection from asbestos-induced cellular damage, we evaluated LGM2605 in asbestos-exposed macrophages from wild-type (WT) and Nrf2 disrupted (Nrf2⁻/⁻) mice. Cells were pretreated with LGM2605 (50 µM and 100 µM) and exposed to asbestos fibers (20 µg/cm²) and evaluated 8 h and 24 h later for inflammasome activation, secreted cytokine levels (interleukin-1β (IL-1β), interleukin-18 (IL-18), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα)), cytotoxicity and cell death, nitrosative stress, and Nrf2-regulated enzyme levels. Asbestos exposure induced robust oxidative and nitrosative stress, cell death and cytotoxicity, which were equally mitigated by LGM2605. Inflammasome activation was significantly attenuated in Nrf2^−/− macrophages compared to WT, and the protective action of LGM2605 was seen only in WT cells. In conclusion, in a cell model of asbestos-induced toxicity, LGM2605 acts via protective mechanisms that may not involve Nrf2 activation.

Secoisolariciresinol diglucoside is a blood-brain barrier protective and anti-inflammatory agent: implications for neuroinflammation

BACKGROUND

Secoisolariciresinol diglucoside (SDG), the main lignan in flaxseed, is known for its beneficial effects in inflammation, oxidative stress, heart disease, tumor progression, atherosclerosis, and diabetes. SDG might be an attractive natural compound that protects against neuroinflammation. Yet, there are no comprehensive studies to date investigating the effects of SDG on brain endothelium using relevant in vivo and in vitro models.

METHODS

We evaluated the effects of orally administered SDG on neuroinflammatory responses using in vivo imaging of the brain microvasculature during systemic inflammation and aseptic encephalitis. In parallel, the anti-inflammatory actions of SDG on brain endothelium and monocytes were evaluated in vitro blood-brain barrier (BBB) model. Multiple group comparisons were performed by one-way analysis of variance with Dunnet's post hoc tests.

RESULTS

We found that SDG diminished leukocyte adhesion to and migration across the BBB in vivo in the setting of aseptic encephalitis (intracerebral TNFα injection) and prevented enhanced BBB permeability during systemic inflammatory response (LPS injection). In vitro SDG pretreatment of primary human brain microvascular endothelial cells (BMVEC) or human monocytes diminished adhesion and migration of monocytes across brain endothelial monolayers in conditions mimicking CNS inflammatory responses. Consistent with our in vivo observations, SDG decreased expression of the adhesion molecule, VCAM1, induced by TNFα, or IL-1β in BMVEC. SDG diminished expression of the active form of VLA-4 integrin (promoting leukocyte adhesion and migration) and prevented the cytoskeleton changes in primary human monocytes activated by relevant inflammatory stimuli.

CONCLUSION

This study indicates that SDG directly inhibits BBB interactions with inflammatory cells and reduces the inflammatory state of leukocytes. Though more work is needed to determine the mechanism by which SDG mediates these effects, the ability of SDG to exert a multi-functional response reducing oxidative stress, inflammation, and BBB permeability makes it an exciting potential therapeutic for neuroinflammatory diseases. SDG can serve as an anti-inflammatory and barrier-protective agent in neuroinflammation.

Synthetic Secoisolariciresinol Diglucoside (LGM2605) Protects Human Lung in an Ex Vivo Model of Proton Radiation Damage

Radiation therapy for the treatment of thoracic malignancies has improved significantly by directing of the proton beam in higher doses on the targeted tumor while normal tissues around the tumor receive much lower doses. Nevertheless, exposure of normal tissues to protons is known to pose a substantial risk in long-term survivors, as confirmed by our work in space-relevant exposures of murine lungs to proton radiation. Thus, radioprotective strategies are being sought. We established that LGM2605 is a potent protector from radiation-induced lung toxicity and aimed in the current study to extend the initial findings of space-relevant, proton radiation-associated late lung damage in mice by looking at acute changes in human lung. We used an ex vivo model of organ culture where tissue slices of donor living human lung were kept in culture and exposed to proton radiation. We exposed donor human lung precision-cut lung sections (huPCLS), pretreated with LGM2605, to 4 Gy proton radiation and evaluated them 30 min and 24 h later for gene expression changes relevant to inflammation, oxidative stress, and cell cycle arrest, and determined radiation-induced senescence, inflammation, and oxidative tissue damage. We identified an LGM2605-mediated reduction of proton radiation-induced cellular senescence and associated cell cycle changes, an associated proinflammatory phenotype, and associated oxidative tissue damage. This is a first report on the effects of proton radiation and of the radioprotective properties of LGM2605 on human lung.

The Synthetic Lignan Secoisolariciresinol Diglucoside Prevents Asbestos-Induced NLRP3 Inflammasome Activation in Murine Macrophages

BACKGROUND

The interaction of asbestos with macrophages drives two key processes that are linked to malignancy: (1) the generation of reactive oxygen species (ROS)/reactive nitrogen species (RNS) and (2) the activation of an inflammation cascade that drives acute and chronic inflammation, with the NLRP3 inflammasome playing a key role. Synthetic secoisolariciresinol diglucoside (SDG), LGM2605, is a nontoxic lignan with anti-inflammatory and antioxidant properties and was evaluated for protection from asbestos in murine peritoneal macrophages (MF).

METHODS

MFs were exposed to crocidolite asbestos ± LGM2605 given 4 hours prior to exposure and evaluated at various times for NLRP3 expression, secretion of inflammasome-activated cytokines (IL-1β and IL-18), proinflammatory cytokines (IL-6, TNFα, and HMGB1), NF-κB activation, and levels of total nitrates/nitrites.

RESULTS

Asbestos induces a significant (p < 0.0001) increase in the NLRP3 subunit, release of proinflammatory cytokines, NLRP3-activated cytokines, NF-κB, and levels of nitrates/nitrites. LGM2605 significantly reduced NLRP3 ranging from 40 to 81%, IL-1β by 89-96%, and TNFα by 67-78%, as well as activated NF-κB by 48-49% while decreasing levels of nitrates/nitrites by 85-93%.

CONCLUSIONS

LGM2605 reduced asbestos-induced NLRP3 expression, proinflammatory cytokine release, NF-κB activation, and nitrosative stress in MFs supporting its possible use in preventing the asbestos-induced inflammatory cascade leading to malignancy.

Enterolactone alters FAK-Src signaling and suppresses migration and invasion of lung cancer cell lines

Background

Systemic toxicity of chemotherapeutic agents and the challenges associated with targeting metastatic tumors are limiting factors for current lung cancer therapeutic approaches. To address these issues, plant-derived bioactive components have been investigated for their anti-cancer properties because many of these agents are non-toxic to healthy tissues. Enterolactone (EL) is a flaxseed-derived mammalian lignan that has demonstrated anti-migratory properties for various cancers, but EL has not been investigated in the context of lung cancer, and its anticancer mechanisms are ill-defined. We hypothesized that EL could inhibit lung cancer cell motility by affecting the FAK-Src signaling pathway.

Methods

Non-toxic concentrations of EL were identified for A549 and H460 human lung cancer cells by conducting 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Dephenyltetrazolium Bromide (MTT) assays. The anti-migratory and anti-invasive potential of EL for lung cancer cell lines was determined by scratch wound healing and Matrigel® invasion assays. Changes in filamentous actin (F-actin) fiber density and length in EL-treated cells were determined using phalloidin-conjugated rhodamine dye and fluorescent microscopy. Vinculin expression in focal adhesions upon EL treatment was determined by immunocytochemistry. Gene and protein expression levels of FAK-Src signaling molecules in EL-treated lung cancer cells were determined using PCR arrays, qRT-PCR, and western blotting.

Results

Non-toxic concentrations of EL inhibited lung cancer cell migration and invasion in a concentration- and time-dependent manner. EL treatment reduced the density and number of F-actin fibers in lung cancer cell lines, and reduced the number and size of focal adhesions. EL decreased phosphorylation of FAK and its downstream targets, Src, paxillin, and decreased mRNA expression of cell motility-related genes, RhoA, Rac1, and Cdc42 in lung cancer cells.

Conclusions

Our data suggest that EL suppresses lung cancer cell motility and invasion by altering FAK activity and subsequent activation of downstream proteins needed for focal adhesion formation and cytoskeletal rearrangement. Therefore, administration of EL may serve as a safe and complementary approach for inhibiting lung tumor cell motility, invasion, and metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1512-3) contains supplementary material, which is available to authorized users.

Tanshinone IIA sensitizes oral squamous cell carcinoma to radiation due to an enhanced autophagy

PURPOSE

Tanshinone IIA (TanIIA), which is derived from the roots of Salvia miltiorrhiza (Danshen), has multiple pharmacological activities. However, the radiosensitivezing activity of TanIIA in oral cancer cells has not been studied extensively. The purpose of this study is to investigate the radiosensitizing effects of TanIIA in human oral squamous cell carcinoma SCC090 and examined the underlying mechanisms.

METHODS

Clonogenic assay was used to investigate the radiosensitizing effect of TanIIA on SCC090. And then, apoptosis and reactive oxygen species (ROS) induced by the combination of TanIIA with radiation were analyzed by Flow cytometry. Finally, autophagy was detected by monodansylcadervarine (MDC) staining.

RESULTS

TanIIA could significantly sensitize SCC090 to radiation. Meanwhile, an increase ROS generation after exposed to the combination treatment was found. In addition, the protein levels of Beclin 1, Atg5 and LC3-II, three important proteins involved in autophagy were increased in cells.

CONCLUSIONS

TanIIA exerted a strong radiosensitizing effect on SCC090 comparing with the simple drug or single radiation treatment, which was due to an enhanced ROS generation and autophagy.

Novel Double-Hit Model of Radiation and Hyperoxia-Induced Oxidative Cell Damage Relevant to Space Travel

Spaceflight occasionally requires multiple extravehicular activities (EVA) that potentially subject astronauts to repeated changes in ambient oxygen superimposed on those of space radiation exposure. We thus developed a novel in vitro model system to test lung cell damage following repeated exposure to radiation and hyperoxia. Non-tumorigenic murine alveolar type II epithelial cells (C10) were exposed to >95% O₂ for 8 h only (O₂), 0.25 Gy ionizing γ-radiation (IR) only, or a double-hit combination of both challenges (O₂ + IR) followed by 16 h of normoxia (ambient air containing 21% O₂ and 5% CO₂) (1 cycle = 24 h, 2 cycles = 48 h). Cell survival, DNA damage, apoptosis, and indicators of oxidative stress were evaluated after 1 and 2 cycles of exposure. We observed a significant (p < 0.05) decrease in cell survival across all challenge conditions along with an increase in DNA damage, determined by Comet analysis and H2AX phosphorylation, and apoptosis, determined by Annexin-V staining, relative to cells unexposed to hyperoxia or radiation. DNA damage (GADD45α and cleaved-PARP), apoptotic (cleaved caspase-3 and BAX), and antioxidant (HO-1 and Nqo1) proteins were increased following radiation and hyperoxia exposure after 1 and 2 cycles of exposure. Importantly, exposure to combination challenge O₂ + IR exacerbated cell death and DNA damage compared to individual exposures O₂ or IR alone. Additionally levels of cell cycle proteins phospho-p53 and p21 were significantly increased, while levels of CDK1 and Cyclin B1 were decreased at both time points for all exposure groups. Similarly, proteins involved in cell cycle arrest was more profoundly changed with the combination challenges as compared to each stressor alone. These results correlate with a significant 4- to 6-fold increase in the ratio of cells in G2/G1 after 2 cycles of exposure to hyperoxic conditions. We have characterized a novel in vitro model of double-hit, low-level radiation and hyperoxia exposure that leads to oxidative lung cell injury, DNA damage, apoptosis, and cell cycle arrest.

Asbestos Induces Oxidative Stress and Activation of Nrf2 Signaling in Murine Macrophages: Chemopreventive Role of the Synthetic Lignan Secoisolariciresinol Diglucoside (LGM2605)

The interaction of asbestos fibers with macrophages generates harmful reactive oxygen species (ROS) and subsequent oxidative cell damage that are key processes linked to malignancy. Secoisolariciresinol diglucoside (SDG) is a non-toxic, flaxseed-derived pluripotent compound that has antioxidant properties and may thus function as a chemopreventive agent for asbestos-induced mesothelioma. We thus evaluated synthetic SDG (LGM2605) in asbestos-exposed, elicited murine peritoneal macrophages as an in vitro model of tissue phagocytic response to the presence of asbestos in the pleural space. Murine peritoneal macrophages (MFs) were exposed to crocidolite asbestos fibers (20 µg/cm²) and evaluated at various times post exposure for cytotoxicity, ROS generation, malondialdehyde (MDA), and levels of 8-iso Prostaglandin F2α (8-isoP). We then evaluated the ability of LGM2605 to mitigate asbestos-induced oxidative stress by administering LGM2605 (50 µM) 4-h prior to asbestos exposure. We observed a significant (p < 0.0001), time-dependent increase in asbestos-induced cytotoxicity, ROS generation, and the release of MDA and 8-iso Prostaglandin F2α, markers of lipid peroxidation, which increased linearly over time. LGM2605 treatment significantly (p < 0.0001) reduced asbestos-induced cytotoxicity and ROS generation, while decreasing levels of MDA and 8-isoP by 71%–88% and 41%–73%, respectively. Importantly, exposure to asbestos fibers induced cell protective defenses, such as cellular Nrf2 activation and the expression of phase II antioxidant enzymes, HO-1 and Nqo1 that were further enhanced by LGM2605 treatment. LGM2605 boosted antioxidant defenses, as well as reduced asbestos-induced ROS generation and markers of oxidative stress in murine peritoneal macrophages, supporting its possible use as a chemoprevention agent in the development of asbestos-induced malignant mesothelioma.