Modification in the ascorbate-glutathione cycle leads to a better acclimation to high light in the rose Bengal resistant mutant of Nannochloropsis oceanica.

Understanding how to adapt outdoor cultures of Nannochloropsis oceanica to high light (HL) is vital for boosting productivity. The N. oceanica RB2 mutant, obtained via ethyl methanesulfonate mutagenesis, was chosen for its tolerance to Rose Bengal (RB), a singlet oxygen (1O2) generator. Compared to the wild type (WT), the RB2 mutant showed higher resilience to excess light conditions. Analyzing the ascorbate-glutathione cycle (AGC), involving ascorbate peroxidases (APX, EC 1.11.1.11), dehydroascorbate reductase (DHAR, EC 1.8.5.1), and glutathione reductase (GR, EC 1.8.1.7), in the RB2 mutant under HL stress provided valuable insights. At 250 µmol photon m-2 s-1 (HL), the WT strain displayed superoxide anion radicals (O2▪-) and hydrogen peroxide (H2O2) accumulation, increased lipid peroxidation, and cell death compared to normal light (NL) conditions (50 µmol photon m-2 s-1). The RB2 mutant didn't accumulate O2▪- and H2O2 after HL exposure, and exhibited increased APX, DHAR, and GR activities and transcript levels compared to WT and remained consistent after HL treatment. Although the RB2 mutant had a smaller ascorbate (AsA) pool than the WT, its ability to regenerate dehydroascorbate (DHA) increased post HL exposure, indicated by a higher AsA/DHA ratio. Additionally, under HL conditions, the RB2 mutant displayed an improved glutathione (GSH) regeneration rate (GSH/GSSG ratio) without changing the GSH pool size. Remarkably, H2O2 or menadione (a O2▪- donor) treatment induced cell death in the WT strain but not in the RB2 mutant. These findings emphasize the essential role of AGC in the RB2 mutant of Nannochloropsis in handling photo-oxidative stress.

Carboxylated Pocoa polysaccharides inhibited oxidative damage and inflammation of HK-2 cells induced by calcium oxalate nanoparticles.

The inhibitory effects of Chinese medicine Pocoa (PCPs) with different carboxyl group (-COOH) contents on oxidative damage and inflammatory response of renal epithelial cells and the influence of -COOH content in polysaccharides were investigated. HK-2 cell damage model was established by nanocalcium oxalate crystals (nanoCOM), and then PCPs with -COOH contents of 2.56% (PCP0), 7.48% (PCP1), 12.07% (PCP2), and 17.18% (PCP3) were used to protect the cells. PCPs could inhibit the damage of nanoCOM to HK-2 cells, increase cell viability, restore cytoskeleton and morphology, and improve lysosomal integrity. PCPs can reduce the oxidative stress response of nanoCOM to cells, inhibit the opening of mPTP and cell necrotic apoptosis, reduce the level of Ca2+ ions in cells, the production of ATP and MDA, and increase SOD expression. PCPs can also reduce the cellular inflammatory response caused by oxidative damage, and reduce the expression of nitric oxide (NO), inflammatory factors TNF-α, IL-6, IL-1ß and MCP-1, as well as the content of inflammasome NLRP3. After protection, PCPs can inhibit the endocytosis of nanoCOM crystals by cells. With the increase in -COOH content in PCPs, its ability to inhibit nanoCOM cell damage, reduce oxidative stress, reduce inflammatory response, and inhibit crystal endocytosis increases, that is, PCP3 with the highest -COOH content, shows the best biological activity. Inhibiting cell damage and inflammation and reducing a large amount of endocytosis of crystals by cells are beneficial to inhibit the formation of kidney stones.

Sulfated Undaria pinnatifida Polysaccharide Promotes Endocytosis of Nano-Calcium Oxalate Dihydrate by Repairing Subcellular Organelles in HK-2 Cells.

The clinical manifestation of primary hyperoxaluria includes hyperoxaluria and recurrent urinary calculi. In this study, an oxidative damage model was constructed based on oxalate damage to the human renal proximal tubular epithelial cells (HK-2), and a comparative study was carried out on four different sulfated levels of Undaria pinnatifida polysaccharides (UPP0, UPP1, UPP2, and UPP3 with sulfate group [-OSO3-] contents of 1.59%, 6.03%, 20.83%, and 36.39%, respectively) on the repair of oxidatively damaged HK-2 cells. The results showed that after repair by UPPs, cell viability was enhanced, healing ability was improved, the intracellular superoxide dismutase level and mitochondrial membrane potential were increased, malondialdehyde, reactive oxygen species, and intracellular Ca2+ levels were reduced, cellular autophagy was reduced; lysosomal integrity was improved, and cytoskeleton and cell morphology were restored. The ability of repaired cells to endocytose nano-calcium oxalate dihydrate crystals (nano-COD) was enhanced. The activity of UPPs was closely related to their -OSO3- content. A too high or too low -OSO3- content was not conducive to polysaccharide activity, and only UPP2 exhibited the best cell repair ability and strongest ability to promote the cell endocytosis of crystals. UPP2 may be used as a potential agent to inhibit CaOx crystal deposition caused by high oxalate concentration.

Antioxidant Activities and Cytotoxicity of the Regulated Calcium Oxalate Crystals on HK-2 Cells of Polysaccharides from Gracilaria lemaneiformis with Different Molecular Weights.

The antioxidant activities of seven degraded products (GLPs) with different molecular weights (Mw) of polysaccharides from Gracilaria lemaneiformis were compared. The Mw of GLP1-GLP7 were 106, 49.6, 10.5, 6.14, 5.06, 3.71 and 2.42 kDa, respectively. The results show that GLP2 with Mw = 49.6 kDa had the strongest scavenging capacity for hydroxyl radical, DPPH radical, ABTS radical and reducing power. When Mw < 49.6 kDa, the antioxidant activity of GLPs increased with the increase in Mw, but when Mw increased to 106 kDa, their antioxidant activity decreased. However, the ability of GLPs to chelate Fe2+ ions increased with the decrease in polysaccharide Mw, which was attributed to the fact that the polysaccharide active groups (-OSO3- and -COOH) were easier to expose, and the steric hindrance was smaller when GLPs chelated with Fe2+. The effects of GLP1, GLP3, GLP5 and GLP7 on the crystal growth of calcium oxalate (CaOx) were studied using XRD, FT-IR, Zeta potential and thermogravimetric analysis. Four kinds of GLPs could inhibit the growth of calcium oxalate monohydrate (COM) and induce the formation of calcium oxalate dihydrate (COD) in varying degrees. With the decrease in Mw of GLPs, the percentage of COD increased. GLPs increased the absolute value of the Zeta potential on the crystal surface and reduced the aggregation between crystals. Cell experiments showed that the toxicity of CaOx crystal regulated by GLPs to HK-2 cells was reduced, and the cytotoxicity of CaOx crystal regulated by GLP7 with the smallest Mw was the smallest, which was consistent with the highest SOD activity, the lowest ROS and MDA levels, the lowest OPN expression level and the lowest cell necrosis rate. These results suggest that GLPs, especially GLP7, may be a potential drug for the prevention and treatment of kidney stones.

Sinocurculigo, a new genus of Hypoxidaceae from China based on molecular and morphological evidence.

BACKGROUND: The monocot family Hypoxidaceae consists of nine genera with nearly 200 species. They occur mostly in the Southern Hemisphere with only a few species in the Northern Hemisphere, of which three genera, Hypoxis, Molineria, and Curculigo, with eight species are distributed in China. Recently, we have found a hypoxid-like plant in China that is quite different in floral structure from any of the three genera and even of the known taxa in Hypoxidaceae. METHODOLOGY/PRINCIPAL FINDINGS: In addition to morphological analysis, we performed maximum parsimony, maximum likelihood, and Bayesian inference analyses based on fragments of the chloroplast matK and rbcL genes of 60 taxa in 12 families representing all major clades of the Hypoxidaceae alliance. Results showed that Hypoxidaceae is monophyletic and and that the new plant belongs to it, forming a distinct clade within the family Hypoxidaceae as a sister of Molineria. Phylogeny of the Hypoxidaceae family was constructed based on a combined matrix of the chloroplast rbcL, trnS-G, and trnL-F regions of 59 taxa in Hypoxidaceae and its alliance. Findings of the molecular investigation is consistent with those of the morphological analysis. CONCLUSIONS/SIGNIFICANCE: Based on the results of our molecular and morphological analyses in the present study, we propose a new genus, Sinocurculigo.

Predicted disappearance of Cephalantheropsis obcordata in Luofu Mountain due to changes in rainfall patterns.

BACKGROUND: In the past century, the global average temperature has increased by approximately 0.74°C and extreme weather events have become prevalent. Recent studies have shown that species have shifted from high-elevation areas to low ones because the rise in temperature has increased rainfall. These outcomes challenge the existing hypothesis about the responses of species to climate change. METHODOLOGY/PRINCIPAL FINDINGS: With the use of data on the biological characteristics and reproductive behavior of Cephalantheropsis obcordata in Luofu Mountain, Guangdong, China, trends in the population size of the species were predicted based on several factors. The response of C. obcordata to climate change was verified by integrating it with analytical findings on meteorological data and an artificially simulated environment of water change. The results showed that C. obcordata can grow only in waterlogged streams. The species can produce fruit with many seeds by insect pollination; however, very few seeds can burgeon to become seedlings, with most of those seedlings not maturing into the sexually reproductive phase, and grass plants will die after reproduction. The current population's age pyramid is kettle-shaped; it has a Deevey type I survival curve; and its net reproductive rate, intrinsic rate of increase, as well as finite rate of increase are all very low. The population used in the artificial simulation perished due to seasonal drought. CONCLUSIONS: The change in rainfall patterns caused by climate warming has altered the water environment of C. obcordata in Luofu Mountain, thereby restricting seed burgeoning as well as seedling growth and shortening the life span of the plant. The growth rate of the C. obcordata population is in descending order, and models of population trend predict that the population in Luofu Mountain will disappear in 23 years.