Pleiotropic drug resistant (PDR/ABCG) genes are involved in plant response to biotic and abiotic stresses. In this work, we cloned, from Solanum tuberosum, four PDR/ABCG transporter genes named StPDR1, StPDR2, StPDR3 and StPDR4, which were differentially expressed in plant tissues and cell cultures. A number of different chemically unrelated compounds were found to regulate the transcript levels of the four genes in cultured cells. In particular, StPDR2 was highly up-regulated in the presence of Botrytis cinerea cell walls, NaCl, 2,4-dichlorophenol, sclareol and α-solanin and biological compounds. The expression of the genes was also investigated by real time RT-PCR during infection by Phytophthora infestans. StPDR1 and StPDR2 were up-regulated about 13- and 37-fold at 48 h post-infection (hpi), StPDR3 was expressed (4-5-fold) at 24 and 48 hpi and then rapidly decreased, while StPDR4 RNA accumulation was stimulated (about 4-fold) at 12 and 24 hpi, decreased at 48 hpi and increased again at 96 hpi. We discuss the role of StPDR1-4 genes in response to pathogens and abiotic stresses.

In this study the effects of the glycoalkaloids alpha-solanine, alpha-chaconine, alpha-tomatine and the aglycone solanidine on model membranes composed of PC in the absence and presence of sterols have been analysed via permeability measurements and different biophysical methods. The main result is that glycoalkaloids are able to interact strongly with sterol containing membranes thereby causing membrane disruption in a way which is specific for the type of glycoalkaloid and sterol. For this dual specificity both the sugar moiety of the glycoalkaloid and the side-chain of the sterol on position 24 turned out to be of major importance for the membrane disrupting activity. The order of potency of the glycoalkaloids was alpha-tomatine > alpha-chaconine > alpha-solanine. The plant sterols beta-sitosterol and fucosterol showed higher affinity for glycoalkaloids as compared to cholesterol and ergosterol. The mode of action of the glycoalkaloids is proposed to consist of three main steps:(1) Insertion of the aglycone part in the bilayer.(2) Complex formation of the glycoalkaloid with the sterols present.(3) Rearrangement of the membrane caused by the formation of a network of sterol-glycoalkaloid complexes resulting in a transient disruption of the bilayer during which leakage occurs.

The infectivity of herpes simplex virus Type I in tissue culture was inhibited by prior incubation with aqueous suspensions of glycoalkaloids in order of activity alpha-chaconine greater than alpha-tomatine greater than alpha-solasonine but not by the corresponding aglycones, solanidine, tomatidine and solasodine. However, inhibition was not only dependent on the presence of a sugar moiety since the glycone alpha-solanine was inactive under the conditions used. The glycones, but not the aglycones, showed cytopathic effects on cellular membranes of Vero cells and erythrocytes; therefore, it is suggested that inactivation of virus results from insertion of the glycones into the viral envelope.

BACKGROUND Disruption of epithelial barrier integrity is important in the initiation and cause of inflammatory bowel disease (IBD). Glycoalkaloids, solanine (S), and chaconine (C) are naturally present in potatoes, can permeabilize cholesterol-containing membranes, and lead to disruption of epithelial barrier integrity. Frying potatoes concentrates glycoalkaloids. Interestingly, the prevalence of IBD is highest in countries where fried potatoes consumption is highest. OBJECTIVE To further understand the role of potato glycoalkaloids on intestinal barrier integrity, we examined the effect of varying concentrations of solanine and chaconine on intestinal permeability and function. METHODS Solanine (0-50 microM), chaconine (0-20 microM), or a 1:1 mixture (0-20 microM) were exposed to T84 cultured epithelial monolayers for varying periods of time to determine concentration response effect on epithelial permeability. Next, a 1:1 mixture (5 microM) of solanine-to-chaconine (C:S) was exposed to sheets of normal murine small intestine, mounted in Ussing chambers, from control and interleukin-10 gene-deficient mice to determine whether glycoalkaloids affected intestine from mice with a genetic predisposition for IBD greater than controls. Finally, the effects of glycoalkaloids on colonic histologic injury were examined in mice orally fed amounts of glycoalkaloids that would normally be consumed in a human diet. RESULTS Glycoalkaloids embedded and permeabilized the T84 monolayer epithelial membrane bilayer in a concentration-dependent fashion, with C:S > C > S. In vitro Ussing chamber experiments also illustrated a concentration-dependent disruption of intestinal barrier integrity in animals with a genetic predisposition to develop IBD, but not in control animals. Similarly, in vivo oral feeding experiments demonstrated that C:S ingestion, at physiologic concentrations, aggravated histologic colonic injury in mice genetically predisposed to developing IBD. CONCLUSION Concentrations of glycoalkaloids normally available while eating potatoes can adversely affect the mammalian intestine and can aggravate IBD.

BACKGROUND The duration of action for many pharmaceutical agents is dependent on their breakdown by endogenous hydrolytic enzymes. Dietary factors that interact with these enzyme systems may alter drug efficacy and time course. Cholinesterases such as acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) hydrolyze and inactivate several anesthetic drugs, including cocaine, heroin, esmolol, local ester anesthetics, and neuromuscular blocking drugs. Natural glycoalkaloid toxins produced by plants of the family Solanaceae, which includes potatoes and tomatoes, inhibit both AChE and BuChE. Here the authors assess the extent to which two solanaceous glycoalkaloids (SGAs), alpha-solanine and alpha-chaconine, can alter the effects of neuromuscular blocking drugs and cholinesterase inhibitors in vivo and in vitro. METHODS Inhibition of purified human AChE and BuChE by SGAs, neuromuscular blocking drugs, and cholinesterase inhibitors was assessed by an in vitro colorimetric cholinesterase assay. In vivo experiments were carried out using anesthetized rabbits to test whether SGAs affect recovery from mivacurium-induced paralysis. RESULTS SGAs inhibited human BuChE at concentrations similar to those found in serum of individuals who have eaten a standard serving of potatoes. Coapplication of SGAs (30-100 nm) with neuromuscular blocking drugs and cholinesterase inhibitors produced additive cholinesterase inhibition. SGA administration to anesthetized rabbits inhibited serum cholinesterase activity and mivacurium hydrolysis. In addition, SGA prolonged the time needed for recovery from mivacurium-induced paralysis (149 +/- 12% of control; n = 12). CONCLUSIONS These findings support the hypothesis that inhibition of endogenous enzyme systems by dietary factors can influence anesthetic drug metabolism and duration of action. Diet may contribute to the wide variation in recovery time from neuromuscular blockade seen in normal, healthy individuals.

The purpose of these experiments was to determine the reversibility of alpha-chaconine and alpha-solanine inhibition of human plasma butyrylcholinesterase (BuChE). For the substrate alpha-naphthylacetate, optimal assay conditions were 0.50 M sodium phosphate buffer and a substrate concentration of 3-5 x 10(-4) M. Dibucaine (1 x 10(-5) M) indicated the usual phenotype for all subjects; alpha-chaconine and alpha-solanine at 2.88 x 10(-6) M inhibited BuChE about 70 and 50%, respectively. One- and 24-hr incubations at 1 x 10(-5) M with alpha-chaconine, alpha-solanine, paraoxon, eserine, and ethanol yielded reversible inhibition with dilution except for paraoxon. Twenty-four-hour dialyses of incubations showed no inhibition except for paraoxon. PAGE enzyme activity gels of 1- and 24-hr incubations also showed no inhibition except for paraoxon. alpha-Chaconine and alpha-solanine are reversible inhibitors of human butyrylcholinesterase. At estimated tissue levels, alpha-chaconine, alpha-solanine, and solanidine inhibited BuChE 10-86%. In assays which combined alpha-chaconine, alpha-solanine, and solanidine, inhibition of BuChE was less than additive. No inhibition of albumin alpha-naphthylacetate esterase (an arylesterase) was noted with any inhibitor. The importance of these data to adverse toxicological effects of potato alkaloids is discussed.

Reduced liver weight was used to evaluate the potential toxicity in mice of four naturally occurring steroidal glycoalkaloids: alpha-chaconine and alpha-solanine, alpha-tomatine and solasonine. Increased liver weights was used to evaluate the three corresponding steroidal aglycones: solanidine, tomatidine, and solasodine and the non-alkaloid adrenal steroid dehydroepiandrosterone (DHEA). Adult female Swiss-Webster mice were fed diets containing test compound concentrations of 0 (control), 1.2, 2.4 or 4.8 mmol/kg diet for 7, 14 or 28 d. Absolute liver weights (LW) and relative liver weights (liver weight/body weight x 100,%LW/BW) were determined at autopsy. The %LW/BW was lower than that of controls in mice fed the potato glycoalkaloid alpha-chaconine (-10%, P < or = 0.05) for 7 d with the 2.4 mmol/kg diet dose. Under these same conditions,%LW/BW was greater than that of controls in mice fed two aglycones: solanidine (27%, P < or = 0.001) and solasodine (8%, P < or = 0.01). Relative liver weight increases induced by the aglycones were determined under time and dose conditions in which differences in body weight and food consumption were not significant (2.4 mmol/kg diet for 28 d). Under these conditions, the observed %LW/BW increases relative to the controls were as follows: solanidine (32%, P < or = 0.001), solasodine (22%, P < or = 0.001) and DHEA (16%, P < or = 0.001). Solanidine, solasodine and DHEA were equally potent and were more potent than tomatidine. We also observed that the greater %LW/BW in mice fed 2.4 mmol/kg diet solasodine or solanidine for 14 d declined to near control values if they were fed control diets for another 14 d. The increase in relative liver weight induced by solanidine and solasodine is a reversible adaptive response. These findings and the apparent effects of structure on biological activity should serve as a guide for the removal of the most toxic ++compounds from plant foods. The implications of the results for food safety and health are discussed.

1. In utero exposure to poisons and drugs (e.g., anticholinesterases, cocaine) is frequently associated with spontaneous absorption and placental malfunction. The major protein interacting with these compounds is butyrylcholinesterase (BuChE), which attenuates the effects of such xenobiotics by their hydrolysis or sequestration. Therefore, we studied BuChE expression during placental development. 2. RT-PCR revealed both BuChEmRNA and acetylcholinesterase (AChE) mRNA throughout gestation. However, cytochemical staining detected primarily BuChE activity in first-trimester placenta but AChE activity in term placenta. 3. As the atypical variant of BuChE has a narrower specificity for substrates and inhibitors than the normal enzyme, we investigated its interactions with alpha-solanine and cocaine, and sought a correlation between the occurrence of this variant and placental malfunction. 4. Atypical BuChE of serum or recombinant origin presented > 10-fold weaker affinities than normal BuChE for cocaine and alpha-solanine. However, BuChE in the serum of the heterozygote and a homozygous normal were similar in their drug affinities. Therefore, heterozygous serum or placenta can protect the fetus from drug or poison exposure, unlike homozygous atypical serum or placenta. 5. Genotype analyses revealed that heterozygous carriers of atypical BuChE were threefold less frequent among 49 patients with placental malfunction than among 76 controls of the entire Israeli population. These observations exclude heterozygote carriers of atypical BuChE from being at high risk for placental malfunction under exposure to anticholinesterases.

Solanine is a toxic glycoalkaloid known to accumulate under certain conditions in potato plant, sprouts and tuber in levels which, if ingested, may cause poisoning in humans and farm animals. However, ingested solanine is relatively less toxic than the parenterally administered compound, probably because of its poor absorption, rapid excretion and hydrolysis to less toxic solanine in stomach. Nevertheless, solanine poisoning may cause a gastrointestinal, nervous and exanthematous syndrome severe enough to be fatal. Implications of solanine toxicity in farm animals and humans are discussed in this overview.

The nightshade (Solanum nigrum Linn.) has been widely used in Chinese traditional medicine as a remedy for the treatment of digestive system cancer. The anti-tumor activity of solanine, a steroid alkaloid isolated from the nightshade has been demonstrated. To observe the effect of anti-tumor and mechanism of solanine. The MTT assay was used to evaluate the IC(50) on the three digestive system tumor cell lines. The effect on the morphology was observed with a laser confocal microscopy; the rate of apoptosis and the cell cycle were measured using flow cytometry (FCM); the expression of Bcl-2 protein was measured by Western blot. The results show that the IC(50) for HepG(2), SGC-7901, and LS-174 were 14.47,>50, and >50 microg/ml, respectively; the morphology of cells in the negative control was normal; for the treated groups, typical signs for apoptosis were found. The rate of apoptosis in HepG(2) cells induced by solanine was found to be 6.0, 14.4, 17.3, 18.9, and 32.2%, respectively. Observation of the cell cycle showed that cells in the G(2)/M phases disappeared while the number of cells in the S phase increased significantly for treated groups. Western blot showed that solanine decreased the expression of Bcl-2 protein. Therefore, the target of solanine in inducing apoptosis in HepG(2) cells seems to be mediated by the inhibition in the expression of Bcl-2 protein.