The impacts of exogenous phosphorus on Cd absorption in perennial ryegrass root cell: Kinetic and mechanism study.

Phosphorus (P) is critical to plants in metal-contaminated soils because it participates in various biochemical reactions during plant growth. However, the mechanisms of P in mitigating the toxicity of heavy metals to ryegrass root is still veiled. In this study, the physiological and biochemical dynamics of the ryegrass root under various cadmium (Cd) and P conditions were investigated in a hydroponic system. Cd stress decreased the length of the ryegrass root, but P application enhanced the root elongation to reduce the Cd concentration in the root. Both Cd and P dosages were positively correlated with hemicellulose 1 content, pectin content, and PME activity, while having a negative effect on cellulose content. Moreover, the addition of 80 mg L-1 P increased the contents of pectin and hemicellulose 1 by 2.5 and 5.8% even with 4 mg L-1 Cd. In addition, P supply increased pectin methylesterbase activity under Cd stress, which further changed the extra-cytoplasmic structures and cell wall composition. Thus, exogenous P promoted the immobilization of Cd onto the cell wall and protected protoplast primarily through indirectly regulating the binding capacity of the root cell wall for Cd.

Sufficient Phosphorus Enhances Resistance and Changes Accumulation of Lead in Chlamydomonas reinhardtii.

Phosphorus (P) is critical for algal growth and resistance to environmental stress. However, little is known about the effects of P supply on the lead (Pb) toxicity and accumulation in microalgae. We set up two P concentrations, 315 (PL ) and 3150 µg L-1 (PH ), in algal culture, and the responses of Chlamydomonas reinhardtii to various Pb treatments (0, 200, 500, 1000, 2000, and 5000 µg L-1 ) were investigated. Compared with the PL condition, PH promoted cell growth but reduced cellular respiration by approximately 50%. Moreover, PH alleviated damage to the photosynthetic system in algal cells after Pb stress. After exposure to 200-2000 µg L-1 Pb, higher Pb2+ concentrations and Pb removal were observed in the PL medium. However, under exposure to 5000 µg L-1 Pb, less Pb2+ was present but more Pb was removed by the algal cells in the PH medium. More P supply enhanced the secretion of extracellular fluorescent substances by C. reinhardtii. Transcriptomic analysis showed that genes associated with synthesis of phospholipids, tyrosine-like proteins, ferredoxin, and RuBisCO were up-regulated after Pb exposure. Together the findings of our study demonstrated the critical roles of P in Pb accumulation and resistance in C. reinhardtii. Environ Toxicol Chem 2023;42:1960-1970. © 2023 SETAC.

Evaluating the potential of charred bone as P hotspot assisted by phosphate-solubilizing bacteria.

The enhanced phosphorus (P) release from charred bone by microorganisms results in hotspots to alleviate P limitation in agricultural and natural systems. This study compared P release, assisted by phosphate-solubilizing bacteria (PSB), from charred bone (CB) produced at various temperatures (100-300 °C). In the absence of PSB, soluble P from CB in water was observed with fluctuation between 100 and 300 °C, with a maximum value of 8.66 mg/L at 200 °C. Similarly, kinetics of dissolution indicated that CB produced at 250 °C owned the highest solubility and dissolution rate. After the addition of PSB, soluble P from all the CB samples were all elevated. The CB produced at 100 °C incredibly showed the most significant enhancement (from 3.51 to 77.37 mg /L). ATR-IR and XPS confirmed the loss of organic matter (primarily collagen), but no significant mineralogical alternation of bioapatite in bone. Meanwhile, it demonstrated that collagen itself cannot provide soluble P. However, the collagen contributed to the substantial sorption of bacteria, which improved the efficiency of P release from CB surface. This study clarified the P release via the interaction between CB and PSB, and hence provided a new perspective on understanding P biogeochemical cycle in ecosystem.

Total Flavones of Abelmoschus manihot Exhibits Pro-Angiogenic Activity by Activating the VEGF-A/VEGFR2-PI3K/Akt Signaling Axis.

Angiogenesis is a process of new blood vessel formation from pre-existing vessels. Vascular endothelial growth factor-A (VEGF-A) binds to VEGF receptor-2 (VEGFR2) and thus activation of phosphatidylinositol 3-kinase (PI3K)/Akt pathway play a central role in angiogenesis. Total flavones of Abelmoschus manihot (TFA), the major active component of the traditional Chinese herb Abelmoschus manihot, display novel pro-angiogenic activity. However, little information concerning its underlying mechanism is available. Here we investigate the pro-angiogenesis of TFA with the aim of understanding its mechanism of action. Human umbilical vein endothelial cells (HUVECs) and the chick chorioallantoic membrane (CAM) model were used to evaluate pro-angiogenesis of TFA using cell viability, wounding healing, transwell invasion, tube formation, RT-qPCR and Western blot methods. LY294002, a PI3K inhibitor, was used to interfere with PI3K/Akt pathway signal for assessing the underlying mechanism. Results in vitro indicated TFA obviously promoted HUVECs proliferation, migration, invasion and tube formation. Furthermore, TFA markedly augmented PI3K and Akt phosphorylation and up-regulated VEGF-A and VEGFR2 expression in HUVECs. However, pre-treatment with LY294002 not only markedly attenuated TFA-induced cells proliferation, migration, invasion and tube formation, but also significantly abolished TFA-induced VEGF-A and VEGFR2 over-expression as well as PI3K and Akt phosphorylation. Experiments in CAM model showed TFA significantly promoted the formation of branched blood vessels and was dramatically suppressed by LY294002. Taken together, TFA promoted angiogenesis both in vitro and in vivo which, however, were counteracted by LY294002, suggesting at least in part, TFA exhibits pro-angiogenic activity by activating the VEGF-A/VEGFR2-PI3K/Akt signaling axis.

The cardioprotective effect of total flavonoids on myocardial ischemia/reperfusion in rats.

The flowers of Abelmoschus manihot (L.) Medic is a traditional Chinese medicine used for the treatment of ischemic diseases. The present study is to investigate whether total flavones (TA) of extracted from Abelmoschus manihot L. Medic has the potential cardioprotective effect on myocardial ischemia/reperfusion (I/R) damage in rats. The index of myocardial injury, inflammatory biomarkers and NLRP3-related parameters were measured, respectively. The results demonstrated that compared to I/R group, TA reduced myocardial infarction area, declined serum creatinine kinase (CK), lactate dehydrogenase (LDH) levels, attenuated serum interleukin-6 (IL-6), IL-1ß and tumour necrosis factor (TNF-α) production. Moreover, TA markedly enhanced the activities of superoxide dismutase (SOD) and reduced the amounts of malondialdehyde (MDA) in I/R rats. In addition, TA reduced myocardial I/R induced injury in rats by inhibiting NLRPR3 inflammasome. Thus, it is assumed that TA could significantly improve myocardial I/R injury in rats partially through suppressing NLRP3 activtion.