Wnt/PCP signalling cascade disruption by JNK inhibition as a potential mechanism underlying the teratogenic effects of potato glycoalkaloids.

It is hypothesised that the inhibition of the non-canonical Wnt/PCP intracellular signalling cascade by potato glycoalkaloids, [Formula: see text]-solanine and [Formula: see text]-chaconine, results in an increased risk of neural tube defects (NTDs). One very prominent intracellular signalling pathway with substantial implications in the development and closure of the neural tube is the Wnt/PCP pathway. Experimental inhibition of this results in NTDs. A vital element of this signalling cascade is JNK, which controls the transcription of DNA, which controls cell polarity and directional cell migration. JNK inhibition also results in NTDs experimentally. Through their use in cancer research, [Formula: see text]-solanine and [Formula: see text]-chaconine were found to inhibit metastasis by inhibiting JNK, among other intracellular signalling molecules. Thus, this shows that potato glycoalkaloids increase the likelihood of causing NTDs by inhibiting the proper functioning of JNK in the Wnt/PCP pathway, resulting in defective neural tube closure.

Discovery of a Bacterial Gene Cluster for Deglycosylation of Toxic Potato Steroidal Glycoalkaloids α-Chaconine and α-Solanine.

Potato juice is a byproduct of starch processing currently used as feed. However, potato proteins are an untapped source of high-protein food for human nutrition if harmful constituents notably glycoalkaloids (GAs) are detoxified. The two principle GAs found in potato are α-chaconine and α-solanine, both consisting of a solanidine aglycone with a carbohydrate side chain. The first step in the detoxification of these compounds is the removal of the trisaccharide. Whole-genome sequencing of a bacterial isolate, Arthrobacter sp. S41, capable of completely degrading α-chaconine and α-solanine, revealed the presence of a gene cluster possibly involved in the deglycosylation of GAs. Functional characterization confirmed the enzymatic activity of the gene cluster involved in the complete deglycosylation of both α-chaconine and α-solanine. The novel enzymes described here may find value in the bioconversion of feed proteins to food proteins suitable for human nutrition.

Alpha-solanine inhibits cell proliferation via mitochondrial dysfunction and inhibin synthesis in mouse testis In vitro and In vivo.

Sertoli and Leydig cells provide key supporting roles in spermatogenesis. Various toxins have been studied in the TM3 and TM4 mouse testis cell lines to identify their regulatory effects. Alpha-solanine (α-solanine), a toxic compound found in the potato, has cytotoxic effects on various cells, including cancer cells. However, the effect of α-solanine on testis function has not been identified. In this study, we verified for the first time the anti-proliferative effect of α-solanine in mouse testes. α-Solanine reduced cell viability in TM3 and TM4 cells and reduced the expression of the cell cycle checkpoint genes Ccnd1 and Ccne1. We also detected changes in the mitochondrial membrane potential (MMP) and in the cytosolic calcium and intracellular signal pathways in both cell lines. α-Solanine induced AKT, P70S6K, S6, ERK1/2, and JNK activation in mouse testis cells. In addition, the inhibition of AKT with a pharmacological inhibitor (LY294002) demonstrated more synergic anti-proliferative effects than in the TM3 and TM4 cell lines treated only with α-solanine. Inha and Inhba mRNA expression also decreased in both cell lines and α-solanine i.p. injected mouse testes. Collectively, the results from this study verify the toxic effects of α-solanine on testes and male reproductive function.

α-Solanine impairs oocyte maturation and quality by inducing autophagy and apoptosis and changing histone modifications in a pig model.

In this study, we used a pig model to investigate the effects of α-solanine (a natural toxin found mainly in potato sprouts) on oocyte maturation, quality and subsequent embryonic development. We found that α-solanine (10 µM) disturbed meiotic resumption and increased abnormal spindle formation and altered the cortical granule (CG) distribution compared with the untreated group. α-Solanine triggered autophagy and apoptosis by increasing the expressions of autophagy-related genes (LC3, ATG7, and LAMP2) and apoptotic related genes (BAX and CASP3). Exposure of porcine oocytes to α-solanine significantly increased the levels of H3K36me3 and H3K27me3. Moreover, α-solanine significantly reduced the cleavage and blastocyst formation rates, decreased the total and inner cell mass cells numbers, and increased apoptosis in these porcine embryos. Taken together, our data indicate that α-solanine toxically impairs oocyte maturation and quality by triggering autophagy/apoptosis and facilitating epigenetic modifications. Furthermore, α-solanine suppressed subsequent embryonic development and reduced embryo quality.

Characterization and Transcriptional Profile of Genes Involved in Glycoalkaloid Biosynthesis in New Varieties of Solanum tuberosum L.

Before commercial release, new potato (Solanum tuberosum) varieties must be evaluated for content of toxic compounds such as glycoalkaloids (GAs), which are potent poisons. GA biosynthesis proceeds via the cholesterol pathway to α-chaconine and α-solanine. The goal of this study was to evaluate the relationship between total glycoalkaloid (TGA) content and the expression of GAME, SGT1, and SGT3 genes in potato tubers. TGA content was measured by HPLC-MS, and reverse transcription quantitative polymerase chain reactions were performed to determine the relative expression of GAME, SGT1, and SGT3 genes. We searched for cis-elements of the transcription start site using the PlantPAN database. There was a relationship between TGA content and the relative expression of GAME, SGT1, and SGT3 genes in potato tubers. Putative promoter regions showed the presence of several cis-elements related to biotic and abiotic stresses and light. These findings provide an important step toward understanding TGA regulation and variation in potato tubers.

Potato leaf extract and its component, α-solanine, exert similar impacts on development and oxidative stress in Galleria mellonella L.

Plants synthesize a broad range of secondary metabolites that act as natural defenses against plant pathogens and herbivores. Among these, potato plants produce glycoalkaloids (GAs). In this study, we analyzed the effects of the dried extract of fresh potato leaves (EPL) on the biological parameters of the lepidopteran, Galleria mellonella (L.) and compared its activity to one of the main EPL components, the GA α-solanine. Wax moth larvae were reared from first instar on a diet supplemented with three concentrations of EPL or α-solanine. Both EPL and α-solanine affected survivorship, fecundity, and fertility of G. mellonella to approximately the same extent. We evaluated the effect of EPL and α-solanine on oxidative stress in midgut and fat body by measuring malondialdehyde (MDA) and protein carbonyl (PCO) contents, both biomarkers of oxidative damage. We evaluated glutathione S-transferase (GST) activity, a detoxifying enzyme acting in prevention of oxidative damage. EPL and α-solanine altered MDA and PCO concentrations and GST activity in fat body and midgut. We infer that the influence of EPL on G. mellonella is not enhanced by synergistic effects of the totality of potato leaf components compared to α-solanine alone.

Synergistic cytotoxicity induced by α-solanine and α-chaconine.

α-Solanine and α-chaconine are well-known potato toxins, but the mechanism of the synergistic cytotoxic effect of these alkaloids has been little clarified. This study confirmed their synergistic cytotoxic effects on C6 rat glioma cells by three different cell viability tests, namely WST-1 (water-soluble tetrazolium) assay sensitive to intracellular NADH concentration, menadione-catalysed chemiluminescent assay depending on both NAD(P)H concentration and NAD(P)H:quinone reductase activity, and LDH (lactate dehydrogenase) assay sensitive to the release of LDH from damaged cells. The maximum cytotoxic effect was observed at a ratio of 1:1 between α-solanine and α-chaconine at micromolar concentrations. The cytotoxic effects of these alkaloids were observed immediately after incubation and were constant after 30min, suggesting that rapid damage of plasma membrane causes the lethal disorder of metabolism.

Review of the inhibition of biological activities of food-related selected toxins by natural compounds.

There is a need to develop food-compatible conditions to alter the structures of fungal, bacterial, and plant toxins, thus transforming toxins to nontoxic molecules. The term 'chemical genetics' has been used to describe this approach. This overview attempts to survey and consolidate the widely scattered literature on the inhibition by natural compounds and plant extracts of the biological (toxicological) activity of the following food-related toxins: aflatoxin B1, fumonisins, and ochratoxin A produced by fungi; cholera toxin produced by Vibrio cholerae bacteria; Shiga toxins produced by E. coli bacteria; staphylococcal enterotoxins produced by Staphylococcus aureus bacteria; ricin produced by seeds of the castor plant Ricinus communis; and the glycoalkaloid α-chaconine synthesized in potato tubers and leaves. The reduction of biological activity has been achieved by one or more of the following approaches: inhibition of the release of the toxin into the environment, especially food; an alteration of the structural integrity of the toxin molecules; changes in the optimum microenvironment, especially pH, for toxin activity; and protection against adverse effects of the toxins in cells, animals, and humans (chemoprevention). The results show that food-compatible and safe compounds with anti-toxin properties can be used to reduce the toxic potential of these toxins. Practical applications and research needs are suggested that may further facilitate reducing the toxic burden of the diet. Researchers are challenged to (a) apply the available methods without adversely affecting the nutritional quality, safety, and sensory attributes of animal feed and human food and (b) educate food producers and processors and the public about available approaches to mitigating the undesirable effects of natural toxins that may present in the diet.

Compositional and toxicological analysis of a GM potato line with reduced α-solanine content--a 90-day feeding study in the Syrian Golden hamster.

Steroidal glycoalkaloids (GAs) are toxins, produced by plants of the Solanaceae family. The potato plant (Solanum tuberosum L.) and its tubers predominantly contain the two GAs α-chaconine and α-solanine. These compounds are believed to act in synergy, and the degree of toxicity may therefore depend on their ratio in the potato. To determine the influence of α-solanine: α-chaconine ratio in potatoes on toxicity, a GM potato line (SGT 9-2) with reduced α-solanine content, and the parental control line (Desirée wild-type) having a traditional α-solanine: α-chaconine ratio were (1) studied for compositional similarity by analysing for a range of potato constituents, and (2) used in a 90-day feeding trial with the Syrian Golden hamster to study differential toxicity. The animal feeding study used diets with up to 60% freeze-dried potato powder from either line. Whilst data indicated some compositional differences between the GM line and its wildtype control these did not raise concerns related to nutritional value or safety. Results of the feeding trials showed a low number of significant differences between potato lines with different α-solanine: α-chaconine ratio but none were considered to raise safety concerns with regard to human (or animal) consumption.

Degradation of the potato glycoalkaloid alpha-solanine in three agricultural soils.

The toxic glycoalkaloids produced by the potato plant (Solanum tuberosum L.) have previously been found in upper soil from a potato field during several months. Further insight into the fate of the glycoalkaloids is needed, as only little information about their degradation in soil is available. Degradation of the glycoalkaloid, alpha-solanine, has been followed for 42d in three agricultural soils with common texture and carbon contents. A similar degradation pattern was found in all soils, and the kinetics was well described by a sum of two first-order equations. Overall, degradation rates for the initial first reaction were in the range 0.22-1.64d(-1). Estimated half-lives were in the range 1.8-4.1d for the three top soils at 15 degrees C; the fastest degradation was observed in the sandy soil. The major proportion of alpha-solanine in the sandy soil was degraded by the fast process, while the proportion was lower for the two other soils. Fast degradation appeared to be related to the presence of low amount of sorbents. Additionally, degradation was followed at 5 degrees C in A- and C-horizon soil from the sandy location, and for both horizons the half-lives were of similar length (4.7-8.7d). For the slow process, degradation rates were in the range 0.000-0.123d(-1), and residuals were still present in all soils and all temperatures at the end of the experiment (d 42). Overall, fast degradation was found in both top- and subsoil even at low temperatures, and the risk for alpha-solanine leaching to the groundwater appears to be low.

Degradation of the potato glycoalkaloids--alpha-solanine and alpha-chaconine in groundwater.

The potato glycoalkaloids alpha-chaconine and alpha-solanine are produced in high amounts in potato plants from where release to soil takes place. Degradation of the compounds in groundwater was investigated, as their fate in the terrestrial environment is unknown. Abiotic and microbial degradation were followed in groundwater sampled from below a potato field and spiked with the glycoalkaloids (115 nmol/l). Degradation was primarily microbial and the glycoalkaloids were degraded within 21-42 days. The metabolites beta(1)-solanine, gamma-solanine, and solanidine were formed from alpha-solanine, while beta-chaconine, gamma-chaconine and solanidine were detected from alpha-chaconine. Thus, indigenous groundwater microorganisms are capable of degrading the glycoalkaloids.

A 28-day repeat dose toxicity study of steroidal glycoalkaloids, alpha-solanine and alpha-chaconine in the Syrian Golden hamster.

Glycoalkaloids alpha-solanine and alpha-chaconine are naturally present toxicants in the potato plant (Solanumtuberosum). Human intake of high doses of glycoalkaloids has led to acute intoxication, in severe cases coma and death. Previous studies have indicated that the ratio of alpha-solanine to alpha-chaconine may determine the degree and nature of the glycoalkaloid toxicity in potatoes, as the toxicity of the two alkaloids act synergistically. The aim of the present study was to investigate whether an altered ratio of alpha-solanine and alpha-chaconine would reduce the toxicity of the glycoalkaloids. The Syrian Golden hamster was given daily doses of alpha-solanine and alpha-chaconine by gavage for 28 days. Doses of up to 33.3 mg total glycoalkaloids/kg body weight were applied in ratios of 1:3.7 and 1:70 (alpha-solanine:alpha-chaconine). Administration of the highest doses of both ratios resulted in distended and fluid filled small intestines and stomach. Animals receiving the ratio with the reduced content of alpha-solanine were less affected compared to those receiving the other ratio. Gene expression profiling experiments were conducted using RNA from epithelial scrapings from the small intestines of the hamsters administered the highest doses of the glycoalkaloid treatments. In general, more differential gene expression was observed in the epithelial scrapings of the hamsters fed the ratio of 1:3.7. Mostly, pathways involved in lipid and energy metabolism were affected by the ratio of 1:3.7.

Acute toxicity of high doses of the glycoalkaloids, alpha-solanine and alpha-chaconine, in the Syrian Golden hamster.

Sprouted, stressed, or spoiled potato tubers have reportedly led to human acute intoxication, coma, and death when consumed in high amounts. These effects have been attributed to glycoalkaloids (GAs), primarily alpha-solanine and alpha-chaconine, naturally present in all potatoes. The level of GAs in potato tubers has previously been shown to increase substantially as a result of improper handling and postharvest storage. A short-term study was performed to investigate the dose-response profile of alpha-solanine and alpha-chaconine alone or in combination, administered daily by oral gavage to Syrian Golden hamsters. Daily doses of 100 mg of alpha-solanine [kg body weight (BW)] (-1) induced death in two of four hamsters within 4 days, when administered by gavage to female Syrian hamsters. Doses of 100 mg of alpha-chaconine alone or alpha-solanine and alpha-chaconine combined in a ratio of 1:2.5, in doses of 75 or 100 mg (kg BW) (-1), induced death in one of four hamsters within the same period. Animals dosed with alpha-solanine alone or in combination with alpha-chaconine suffered from fluid-filled and dilated small intestines. The GA administration had no effect on acetyl cholinesterase (AChE) or butyryl cholinesterase (BuChE) activity in plasma or brain. Liquid chromatography-mass spectrometry-based metabolomics showed that there was a specific accumulation of alpha-chaconine in the liver tissues. In addition, metabolomics gave direct evidence of glycolytic metabolism of the GA with the beta 1, beta 2, and gamma-GAs detected in the urine and, to a lesser extent, the feces. Doses from 75 mg (kg BW) (-1) of alpha-chaconine, alpha-solanine, or the two compounds combined were potentially lethal within 4-5 days in the Syrian Golden hamster. However, the cause of death in these studies could not be established. No synergistic effects of alpha-solanine combined with alpha-chaconine were evident.

A human dietary risk assessment associated with glycoalkaloid responses of potato to Colorado potato beetle defoliation.

A quantitative human dietary risk assessment was conducted using the glycoalkaloid concentrations measured from tubers of plants defoliated by Colorado potato beetles and undefoliated (control). There was a significantly greater production of glycoalkaloids for defoliated plants compared to control plants for both skin and inner tissue of tubers. The dietary risk posed to different human subgroups associated with the consumption of potatoes was estimated for the 50th, 95th, and 99.9th percentile US national consumption values. Exposures were compared to a toxic threshold of 1.0mg/kg body weight. Defoliation by Colorado potato beetles increased dietary risk by approximately 48%. Glycoalkaloid concentrations within the inner tissue of tubers, including undefoliated controls, exceeded the toxic threshold for all human subgroups at less than the 99.9th percentile of exposure, but not the 95th percentile.

The folic acid analogue methotrexate protects frog embryo cell membranes against damage by the potato glycoalkaloid alpha-chaconine.

As part of an effort to improve the safety of plant foods, a need exists to more clearly delineate the mechanisms of toxicities of glycoalkaloids, which may be present in Solanum plant species such as potatoes, tomatoes and eggplants. Alpha-chaconine is a major glycoalkaloid present in potatoes. To assess the possible influence of structure of pteridine derivatives on toxicity of potato glycoalkaloids, a previous study that demonstrated the protective effects of folic acid against the Solanum glycoalkaloid alpha-chaconine-induced toxicity on Xenopus laevis frog embryo cell membranes was extended to two folate analogues--a synthetic compound widely used as a therapeutic agent methotrexate, and naturally occurring L-monapterin. Adverse effects on embryos were evaluated by observing changes in membrane potentials with an electrochromic dye, di-4-ANEPPS, as a fluorescent probe for the integrity of the membranes. Methotrexate decreased alpha-chaconine-induced polarization, as did folic acid. This decrease may result from an alteration of membrane conformations that prevents the binding of the glycoalkaloid to the membrane receptor sites, and/or from effects on folic acid metabolism. In contrast, L-monapterin did not significantly reduce the alpha-chaconine-induced toxicity. The possible significance of these results to food safety is discussed.

A study of the toxic hazard that might be associated with the consumption of green potato tops.

Eating green potatoes has reportedly led to poisoning attributed to potato glycoalkaloids (PGA), primarily alpha-solanine and alpha-chaconine. Concentrations of PGA increase during the greening of potatoes but are reportedly much higher in potato tops (leaves). As it is known that members of the UK Bangladeshi community consume potato tops, a study of the toxic hazard that may be associated with the consumption of green potato tops has been carried out. PGA in seven potato varieties were determined by HPLC. Tubers protected from light contained 0.05-0.65 mg/100 g alpha-solanine and 0.3-0.63 mg/100 g alpha-chaconine. Concentrations in leaf samples ranged from 0.64 to 22.6 mg alpha-solanine/100 g and 0.06 to 55.7 mg alpha-chaconine/100 g. Aqueous leaf extracts were cytotoxic to Chinese hamster ovary cells and lysed human, rat and hamster blood cells with no difference in sensitivity among species. Oral administration of potato tops to rats, mice and Syrian hamsters had no adverse effects at the highest practicable dose. A mixture of alpha-solanine and alpha-chaconine (1:1, w/w) given orally at doses of up to 50 mg/kg body weight to hamsters had no effect, but a single ip injection of 25 mg/kg body weight or greater was lethal, with bleeding in the gut. High concentrations of cytotoxic PGA were found in some potato tops, but their effect in laboratory animals was minimal. It is concluded that the consumption of moderate quantities of potato tops (2-5 g/kg body weight/day) is unlikely to represent an acute health hazard to humans.

Synergistic interaction of glycoalkaloids alpha-chaconine and alpha-solanine on developmental toxicity in Xenopus embryos.

The embryo toxicities of two major potato glycoalkaloids, alpha-chaconine and alpha-solanine, were examined individually and in mixtures using the frog embryo teratogenesis assay-Xenopus. Calculations of toxic units (TUs) were used to assess possible antagonism, synergism or response addition of several mixtures ranging from approximately 3:1 to 1:20 TUs of alpha-chaconine to alpha-solanine. Some combinations exhibited strong synergism in the following measures of developmental toxicity: (a) 96-hr LC50, defined as the median concentration causing 50% embryo lethality; (b) 96-hr EC50 (malformation), defined as the concentration causing 50% malformation of the surviving embryos; and (c) teratogenic index which is equal to LC50/EC50 (malformation). The results indicated that each of the mixtures caused synergistic mortality or malformation. Furthermore, these studies suggested that the synergism observed for a specific mixture cannot be used to predict possible synergism of other mixtures with different ratios of the two glycoalkaloids; toxicities observed for individual glycoalkaloids may not be able to predict toxicities of mixtures; and specific combinations found in different potato varieties need to be tested to assess the safety of a particular cultivar.

Protective effects of glucose-6-phosphate and NADP against alpha-chaconine-induced developmental toxicity in Xenopus embryos.

In previous studies a metabolic activation system (MAS) composed of Aroclor 1254-induced rat liver microsomes led to an apparent reduction of potato glycoalkaloid developmental toxicity in the frog embryo teratogenesis assay-Xenopus (FETAX). The reasons for this reduction were investigated in this study. The effect of the exogenous MAS on glycoalkaloid developmental toxicity was examined in two experiments in which a concentration series of alpha-chaconine was tested with a MAS with and without a reduced nicotinamide adenine dinucleotide (NADPH) generator system consisting of NADPH, oxidized nicotinamide adenine dinucleotide (NADP), glucose-6-phosphate (G6P) and glucose-6-phosphate dehydrogenase. The NADPH generator system and each of its individual components were tested at a single high concentration of alpha-chaconine to evaluate their potential effects on toxicity. The findings indicated that the protective effect of the MAS was not the result of detoxification by microsomal enzyme systems, but was caused by two components of the NADPH generator system, namely NADP and G6P. G6P was more protective of alpha-chaconine-induced toxicity than NADP at the concentrations tested. Thus, FETAX with a MAS must be performed with appropriate controls that take into account the possible interactions with individual components of the system.

A preliminary assessment of the toxic and mutagenic potential of steroidal alkaloids in transgenic mice.

Impregnated CD2 transgenic mice, which contain multiple copies of a lambda gt10lacZ construct integrated into the genome of each cell, were given a predetermined estimated maximum tolerated dose of several steroidal alkaloids: Solanum glycoalkaloids from potato, alpha-chaconine and alpha-solanine; aglycones, solanidine and solasodine, and a Veratrum alkaloid, jervine. Observations were made of dams and foetuses for indications of toxicity and/or terata; some dam livers and foetuses were assayed for mutagenicity using the lacZ gene. Other dams were gavaged with a single dose of 75 mg all-trans-retinol/kg to serve as a reference teratogen. Unexpectedly, this level of retinol was not clearly teratogenic. The results of both positive and non-positive selection systems showed that the mutation frequencies in the livers of the dams dosed with alpha-chaconine, alpha-solanine and solanidine were three to four times higher than historically normal in the livers of this transgenic mouse strain.