Effects of membrane plant sterols on excitable cell functions

Synergistic effect of β-sitosterol and biochar application for improving plant growth of Thymus vulgaris under heat stress

Climate change has become the global concern due to its drastic effects on the environment. Agriculture sector is the backbone of food security which remains at the disposal of climate change. Heat stress is the is the most concerning effect of climate change which negatively affect the plant growth and potential yields. The present experiment was conducted to assess the effects of exogenously applied β-sitosterol (Bs at 100 mg/L) and eucalyptus biochar (Eb at 5%) on the antioxidants and nutritional status in Thymus vulgaris under heat stressed conditions. The pot experiment was conducted in completely randomize design in which thymus plants were exposed to heat stress (33 °C) and as a result, plants showed a substantial decline in morpho-physiological and biochemical parameters e.g., a reduction of 59.46, 75.51, 100.00, 34.61, 22.65, and 38.65% was found in plant height, shoot fresh weight, root fresh weight, dry shoot weight, dry root weight and leaf area while in Bs + Eb + heat stress showed 21.16, 56.81, 67.63, 23.09, 12.84, and 35.89% respectively as compared to control. In the same way photosynthetic pigments, transpiration rate, plant nutritional values and water potential increased in plants when treated with Bs and Eb in synergy. Application of Bs and Eb significantly decreased the electrolytic leakage of cells in heat stressed thymus plants. The production of reactive oxygen species was significantly decreased while the synthesis of antioxidants increased with the application of Bs and Eb. Moreover, the application Bs and Eb increased the concentration of minerals nutrients in the plant body under heat stress. Our results suggested that application of Bs along with Eb decreased the effect of heat stress by maintaining nutrient supply and enhanced tolerance by increasing the production of photosynthetic pigments and antioxidant activity.

Context-dependent costs and benefits of endosymbiotic interactions in a ciliate-algae system

Endosymbiosis, an interaction between two species where one lives within the other, has evolved multiple times independently, but the underlying mechanisms remain unclear. Evolutionary theory suggests that for an endosymbiotic interaction to remain stable over time, births of both partners should be higher than their deaths in symbiosis and deaths of both partners should be higher than their births when living independently. However, experimentally measuring this can be difficult and conclusions tend to focus on the host. Using a ciliate-algal system (Paramecium bursaria host and Chlorella endosymbionts), we estimated the benefits and costs of endosymbiosis for both organisms using fitness measurements in different biotic environments to test under which environmental conditions the net effects of the interaction were positive for both partners. We found that the net effects of harbouring endosymbionts were positive for the ciliate hosts as it allowed them to survive in conditions of low-quality bacteria food. The algae benefitted by being endosymbiotic when predators such as the hosts were present, but the net effects were dependent on the total density of hosts, decreasing as hosts densities increased. Overall, we show that including context-dependency of endosymbiosis is essential in understanding how these interactions have evolved.

Biosynthesis and the Roles of Plant Sterols in Development and Stress Responses

Plant sterols are important components of the cell membrane and lipid rafts, which play a crucial role in various physiological and biochemical processes during development and stress resistance in plants. In recent years, many studies in higher plants have been reported in the biosynthesis pathway of plant sterols, whereas the knowledge about the regulation and accumulation of sterols is not well understood. In this review, we summarize and discuss the recent findings in the field of plant sterols, including their biosynthesis, regulation, functions, as well as the mechanism involved in abiotic stress responses. These studies provide better knowledge on the synthesis and regulation of sterols, and the review also aimed to provide new insights for the global role of sterols, which is liable to benefit future research on the development and abiotic stress tolerance in plant.

Plant extracts for developing mosquito larvicides: From laboratory to the field, with insights on the modes of action

In the last decades, major research efforts have been done to investigate the insecticidal activity of plant-based products against mosquitoes. This is a modern and timely challenge in parasitology, aimed to reduce the frequent overuse of synthetic pesticides boosting resistance development in mosquitoes and causing serious threats to human health and environment. This review covers the huge amount of literature available on plant extracts tested as mosquito larvicides, particularly aqueous and alcoholic ones, due to their easy formulation in water without using surfactants. We analysed results obtained on more than 400 plant species, outlining that 29 of them have outstanding larvicidal activity (i.e., LC₅₀ values below 10 ppm) against major vectors belonging to the genera Anopheles, Aedes and Culex, among others. Furthermore, synergistic and antagonistic effects between plant extracts and conventional pesticides, as well as among selected plant extracts are discussed. The efficacy of pure compounds isolated from the most effective plant extracts and - when available - their mechanism of action, as well as the impact on non-target species, is also covered. These belong to the following class of secondary metabolites: alkaloids, alkamides, sesquiterpenes, triterpenes, sterols, flavonoids, coumarins, anthraquinones, xanthones, acetogenonins and aliphatics. Their mode of action on mosquito larvae ranges from neurotoxic effects to inhibition of detoxificant enzymes and larval development and/or midugut damages. In the final section, current drawbacks as well as key challenges for future research, including technologies to synergize efficacy and improve stability - thus field performances - of the selected plant extracts, are outlined. Unfortunately, despite the huge amount of laboratory evidences about their efficacy, only a limited number of studies was aimed to validate their efficacy in the field, nor the epidemiological impact potentially arising from these vector control operations has been assessed. This strongly limits the development of commercial mosquito larvicides of botanical origin, at variance with plant-borne products developed in the latest decades to kill or repel other key arthropod species of medical and veterinary importance (e.g., ticks and lice), as well as mosquito adults. Further research on these issues is urgently needed.

Dietary Phytosterols Protective Against Peptic Ulceration

BACKGROUND

In developing countries the prevalence of duodenal ulceration is related to the staple diet and not to the prevalence of Helicobacter pylori. Experiments using animal peptic ulcer models show that the lipid fraction in foods from the staple diets of low prevalence areas gives protection against ulceration, including ulceration due to non-steroidal anti-inflammatory drugs (NSAIDs), and also promotes healing of ulceration. The lipid from the pulse Dolichos biflorus (Horse gram) was highly active and used for further investigations. Further experiments showed the phospholipids, sterol esters and sterols present in Horse gram lipid were gastroprotective. Dietary phospholipids are known to be protective, but the nature of protective sterols in staple diets is not known. The present research investigates the nature of the protective phytosterols.

METHODS

Sterol fractions were extracted from the lipid in Dolichos biflorus and tested for gastroprotection using the rat ethanol model. The fractions showing protective activity were isolated and identification of the components was investigated by Gas Chromatography-Mass Spectrometry (GC-MS).

RESULTS

The protective phytosterol fraction was shown to consist of stigmasterol, β-sitosterol and a third as yet unidentified sterol, isomeric with β-sitosterol.

CONCLUSIONS

Dietary changes, affecting the intake of protective phospholipids and phytosterols, may reduce the prevalence of duodenal ulceration in areas of high prevalence and may reduce the incidence of recurrent duodenal ulceration after healing and elimination of Helicobacter pylori infection. A combination of phospholipids and phytosterols, such as found in the lipid fraction of ulceroprotecive foods, may be of value in giving protection against the ulcerogenic effect of NSAIDs.

Phytosterols reduce in vitro metastatic ability of MDA-MB-231 human breast cancer cells

Metastasis plays a major role in morbidity and mortality from breast cancer. Differences in the incidence and mortality of breast cancer between societies suggest that environmental factors such as diet may play a role in the disease. Previous work from this laboratory suggests that dietary phytosterols (PS) may offer protection from breast cancer by inhibiting growth of the tumor and its metastasis in severe combined immunodeficient mice. Because metastasis is a multistep process, the aim of the present study was to investigate the effect of PS on some steps of the metastatic process: tumor cell invasion, adhesion, and migration. In addition, cell growth and cell cycle progression were evaluated. MDA-MB-231 cells were supplemented with cholesterol, beta-sitosterol, and campesterol. Cells were treated for 3 days with 16 microM sterol that was loaded on 5 mM cyclodextrin. beta-Sitosterol inhibited tumor cell invasion through Matrigel and adhesion of cells to plates coated with collagen I, collagen IV, fibronectin, and laminin compared with cholesterol treatments and controls. Cholesterol treatment resulted in increased adhesion to laminin and collagen IV, two basement membrane (BM) components that are implicated in signaling tumor cell invasion in this cell line. Only cholesterol treatment increased cellular migration. beta-Sitosterol inhibited cell growth by 70% compared with controls and induced cell cycle arrest at the G2/M phase. It is concluded that, among PS, beta-sitosterol may offer protection from breast cancer metastasis by inhibiting cell invasion of the BM, which may be mediated by its ability to limit the adhesive interaction of the tumor cell and the BM.

Duodenal ulcer prevalence: experimental evidence for the possible role of dietary lipids

BACKGROUND AND AIMS

Mapping the geographical distribution of duodenal ulcer in relation to staple diets, and experiments on animal peptic ulcer models suggested that the lipid fraction in certain foodstuffs had a protective effect which was most marked in the lipid obtained from Horse gram (Dolichos biflorus). Lipid obtained from stored polished rice or rice bran was ulcerogenic. Further animal experiments were designed to investigate the protective and healing effects of Horse gram lipid (HGL) against peptic ulceration.

METHODS

Three effects were investigated in rats: (i) the protective effect of HGL on peptic ulceration produced by using pyloric ligation in combination with South Indian diet or rice bran oil, or by cysteamine, alcohol or aspirin; (ii) the effect of HGL on mast cell degranulation in response to pyloric ligation and rice bran oil; and (iii) the healing effect of HGL on acute gastric ulceration produced by alcohol, on chronic gastric ulceration produced by topical acetic acid or on chronic duodenal ulcer following cysteamine.

RESULTS

Horse gram lipid was shown to be protective and to promote ulcer healing in all the models used. Mast cell degranulation was inhibited.

CONCLUSION

The experiments confirm the presence of a lipid in certain staple foods that have protective and healing properties in experimental peptic ulcer animal models. The differences in the prevalence of duodenal ulceration between different regions in some developing countries with a high prevalence of Helicobacter pylori infection might be explained by the presence or absence of protective lipids or ulcerogenic factors in the staple diet.