Analyzing the role of soil and rice cadmium pollution on human renal dysfunction by correlation and path analysis

Study on remediation of cadmium contaminated paddy field by ramie (Boehmeria nivea L.) floating island and its supporting technology

Ramie (Boehmeria nivea L.) is an ideal crop for cadmium (Cd) pollution remediation due to its advantages of both remediating and utilizing, however, it is mainly carried out in dry land, whose restoration effect is relatively slow. Previously, we found that the ramie plants cultivated by hydroponics has several tens of times higher Cd absorption capacity than that planted in soil. However, the issue of how to use hydroponic ramie to remediate Cd contaminated paddy fields needs to be addressed. In this study, we innovatively developed the ramie floating island technology and studied its remediation model on simulated Cd contaminated paddy fields. Different ramie varieties were used to compare the remediation effects, and the results showed that there were differences in adaptability among different varieties on floating islands and the remediation ability of the tested ramie varieties was Z2 > Z1 > Z3. Different harvested times were set to analyze the effects of harvested model on remediation, and it was suggested that multiple harvests can be carried out according to the plant growth status of ramie floating island after 30 days of remediation to achieve better remediation effects. Low water level height (5 cm) of paddy field was beneficial for the accumulation of Cd in the roots, but considering the adaptability of various ramie varieties and the effect of long-term restoration, it was recommended that the water level height of 20 cm for the cultivation of ramie floating island was more suitable. Moreover, we found that low concentration of citric acid (≤2 g L-1) or polyaspartic acid (≤3 g L-1) can improve the remediation effects for ramie floating island. Our study opens up a novel approach for ramie to remediate heavy metal pollution and provides a technical reference for water body Cd remediation by plants.

A dicyanisophorone-based probe for dual sensing Zn2+ and Cd2+ by near-infrared fluorescence

Zinc ions (Zn²⁺) and cadmium ions (Cd²⁺) are widely present in our production and life, which are closely related to human health and environmental protection. Hence, it is essential to detect their concentrations. Herein, we developed a convenient and reliable small-molecule fluorescent probe based on Schiff base of dicyanisophorone and 2-hydrazinopyridine. This probe can be able to selectively detect Zn²⁺ and Cd²⁺, showing the advantages of near-infrared emission (the maximum emission wavelength: 668 nm), good selectivity, high sensitivity (the detection limits: 0.21 µM and 0.31 µM, respectively) and rapid response (15 s). It has excellent potential for rapid testing and visual tracking of Zn²⁺ and Cd²⁺ in aqueous solution and living cells.

Enhancement of humic acid on plant growth in a Cd-contaminated matrix: performance, kinetics, and mechanism

Phytoremediation of heavy metal-contaminated sites has been widely used. Nonetheless, the destruction of chloroplasts and plant growth enzymes by heavy metals leads to a low germination rate and high mortality of plants. To address these issues, an experiment was conducted in which plants were grown with (SHC) and without humic acid (SC) in actual Cd-contaminated soil from the site of an industrial pollution source. The results showed that the average germination rates of SC and SHC samples were 94.17% and 98.33%, respectively, and the plant heights were approximately 5 and 7 cm after 42 days of planting, respectively. It was discovered that humic acid (HA) enhanced plant growth by increasing urease and invertase content of the soil. The Shannon index and Venn diagram revealed that SHC had the richer population diversity. High-throughput analysis demonstrated that HA increased the content of plant growth-promoting bacteria in the soil from 5.01 to 34.27%. The experimental results revealed that HA increased microbial activity and diversity, thereby providing a favorable environment for plants to thrive. This study develops an effective method to enhance the phytoremediation performance of heavy metal-contaminated soils.

Effect of different amounts of fruit peel-based activator combined with phosphate-solubilizing bacteria on enhancing phytoextraction of Cd from farmland soil by ryegrass

To improve the uptake of heavy metals by plants and increase the effectiveness of phytoextraction, chelating agents are employed to change the speciation of heavy metals in soil and increase their bioavailability. However, the effect of a single activator is limited. In recent years, compound activators have been applied widely to improve phytoextraction efficiency. In this study, a fruit peel-based activator (OG) was prepared, containing a mixture of orange peel extracts and tetrasodium glutamate diacetate (GLDA) (1.6% v/v) in a ratio of 1:1 (v/v). The pot experiment was used to investigate the effects of different amounts of OG combined with phosphate-solubilizing bacteria (Acinetobacter pitti, AP) on the extraction of Cd from farmland soil by ryegrass (Lolium perenne L). The results indicated that the addition of OG and AP increased the pH and EC of the soil and improved the content of nutrient elements in the soil. The optimal combination of the application rates of OG and AP improved the growth of ryegrass and enhanced the phytoextraction of Cd. Redundancy analysis (RDA) showed that total soil nitrogen had the greatest influence on phytoextraction, with a contribution rate of 85.3%, followed by pH, with a contribution rate of 7.7%. Total nitrogen, pH, available phosphorus, alkaline nitrogen, and total organic matter were correlated positively with plant Cd, soil Cd decrease ratio, and the bioaccumulation factor but negatively with total Cd and available Cd. Based on the findings of this study, it is feasible to apply the fruit peel-based activator (amended with GLDA) and phosphate-solubilizing bacteria to enhance phytoextraction of Cd, which will provide a valuable reference for the treatment of heavy metal-contaminated soils and the reutilization of fruit peel waste. When applying the compound activator, it is recommended to consider the influence of the additional amount of compound activator on the extraction efficiency.

Selenium protects against cadmium-induced cardiac injury by attenuating programmed cell death via PI3K/AKT/PTEN signaling

Cadmium (Cd) is an environmental pollutant that has an enormous influence on agricultural production, but selenium (Se) can alleviate its toxicity. The present study aimed to illustrate the effects of Se on Cd-induced heart injury. All 40 rabbits were randomly divided into four groups: control group, Se [0.5 mg kg^-1 ·body weight (BW)] group, Cd (1 mg kg^-1 ·BW) group, and Se + Cd group. After 30 days of feeding, morphological changes, the levels of oxidative stress and myocardial enzyme, the content of cardiac troponin T, programmed cell death (pyroptosis, autophagy and apoptosis), and PI3K/AKT/PTEN transduction capacity were observed. The results showed that Cd destroyed the physiological balance of trace elements and caused myocardial damage, increased the cardiac oxidative damage and led to programmed cell death. Coadministration of Se prominently ameliorated histological lesions and improved cardiac function of hearts in Cd-induced rabbits. Furthermore, Se exerted detoxification and oxidation resistance, maintained trace element homeostasis, and alleviated the changes of mRNA and protein levels of pyroptosis-, autophagy- and apoptosis-controlling factors and PI3K/AKT/PTEN signal molecules caused by Cd. In conclusion, Se might protect against Cd-induced pyroptosis, autophagy and apoptosis by interfering with PI3K/AKT/PTEN signaling in heart.

Speciation, transportation, and pathways of cadmium in soil-rice systems: A review on the environmental implications and remediation approaches for food safety

Cadmium (Cd) contamination in paddy fields is a serious health concern because of its high toxicity and widespread pollution. Recently, much progress has been made in elucidating the mechanisms involved in Cd uptake, transport, and transformation from paddy soils to rice grains, aiming to mitigate the associated health risk; however, these topics have not been critically reviewed to date. Here, we summarized and reviewed the (1) geochemical distribution and speciation of Cd in soil-rice systems, (2) mobilization, uptake, and transport of Cd from soil to rice grains and the associated health risks, (3) pathways and transformation mechanisms of Cd from soil to rice grains, (4) transporters involved in reducing Cd uptake, transport, and accumulation in rice plants, (5) factors governing Cd bioavailability in paddy, and (6) comparison of remediation approaches for mitigating the environmental and health risks of Cd contamination in paddy fields. Briefly, this review presents the state of the art about the fate of Cd in paddy fields and its transport from soil to grains, contributing to a better understanding of the environmental hazards of Cd in rice ecosystems. Challenges and perspectives for controlling Cd risks in rice are thus raised. The summarized findings in this review may help to develop innovative and applicable methods for controlling Cd accumulation in rice grains and sustainably manage Cd-contaminated paddy fields.

Cadmium exposure induces rat proximal tubular cells injury via p62-dependent Nrf2 nucleus translocation mediated activation of AMPK/AKT/mTOR pathway

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a nuclear transcription factor of great concern which is widely involved in physiological and pathological processes of the organism, but the role and regulatory mechanism of Nrf2 in kidney exposed to cadmium (Cd) remain largely unknown. Here we demonstrated that Cd exposure induced injury in primary rat proximal tubular (rPT) cells and NRK-52E cell line, which was accompanied by autophagic flux blockade and subsequent accumulation of p62. Cd-activated nucleus translocation of Nrf2 depended on p62, which promoted antioxidant genes transcription, but it failed to against Cd-induced cell injury and ultimately succumbed to Cd toxicity. CDDO Methyl Ester (CDDO-ME) or ML385 treatment aggravated or alleviated rPT cells injury induced by Cd respectively, indicating that Nrf2 nucleus translocation played a negative role during Cd-induced rPT cells injury. Phosphorylation of 5' AMP-activated protein kinase (AMPK) decreased together with enhanced Nrf2 nucleus translocation in rPT cells exposed to Cd. Dephosphorylation of AMPK induced by Cd were facilitated or restored by CDDO-ME or ML385 treatment, which confirmed AMPK is a downstream factor of Nrf2. Simultaneously, CDDO-ME further enhanced Phosphorylation of mTOR and AKT which increased during Cd exposure. While, Cd-induced phosphorylation of mTOR and AKT were reversed by ML385 treatment. These results illustrated that Cd mediated Nrf2 nucleus translocation depends on p62 accumulation which results from autophagic flux inhibition. The enhanced nucleus translocation of Nrf2 suppresses phosphorylation of AMPK to inactivate AKT/mTOR signaling, and results in rPT cells injury finally.

Cadmium exposure triggers osteoporosis in duck via P2X7/PI3K/AKT-mediated osteoblast and osteoclast differentiation

Cadmium is a common environmental pollutant that accumulates in the bone and kidneys and causes severe health and social problems. However, the effects of Cd on the occurrence of osteoporosis and its mechanism of action in this process are unclear. To test whether Cd-induced osteoporosis is mediated via P2X7/PI3K/AKT signaling, duck bone marrow mesenchymal stem cells (BMSCs) and bone marrow macrophage cells (BMMs) were treated with Cd for 5 days, and duck embryos were treated with Cd_. Micro-CT analysis indicated that Cd-induced osteoporosis occurs in vivo, and histopathology and immunohistochemical analyses also revealed that Cd induced bone damage and the downregulation of osteogenic and bone resorption-related proteins. Cd exposure significantly inhibited the differentiation of BMSCs and BMMs into osteoblasts and osteoclasts in vitro, and promoted osteoblast and osteoclast apoptosis. Cd exposure significantly downregulated the P2X7/PI3K/AKT signaling pathway in vivo and in vitro, and inhibition of this signaling pathway significantly aggravated osteoblast and osteoclast differentiation. Cd exposure also upregulated the OPG/RANKL ratio in vivo and in vitro, further inhibiting osteoclast differentiation. These results demonstrate that Cd causes osteoporosis in duck by inhibiting P2X7/PI3K/AKT signaling and increasing the OPG/RANKL ratio. These results establish a previously unknown mechanism of Cd-induced osteoporosis.

Ectopic expression of SaNRAMP3 from Sedum alfredii enhanced cadmium root-to-shoot transport in Brassica juncea

SaNRAMP3 gene cloned from a Zn/Cd hyperaccumulator Sedum alfredii was ectopicly expressed in Brassica juncea, a fast-growing and high-biomass crop plant. In a tissue culture experiment, transgenic plants were grown on MS medium with 0, 25, 50, 100, 200 μM Cd. It was shown that, at the same Cd treatment, the Cd tolerance of transgenic plants had no significant difference with those of wild-type plants (WT). However, the shoot Cd content and accumulation were improved significantly while the root Cd content and accumulation were descended significantly by SaNRAMP3 gene expression, which obviously enhanced the Cd root-to-shoot translocation factor (TF). In the hydroponic experiment, plants were cultured in nutrition solution with 0, 2.5, 25 μM Cd. Data showed that the Cd tolerance of transgenic plants had no significant difference with that of WT under the same Cd exposure. Whereas, the shoot Cd content and accumulation was increased 1.43-1.81 times and the TF was enhanced 3.09-3.51 times by SaNRAMP3 gene expression. Those results indicated that ectopic expression of SaNRAMP3 in B. juncea didn't lead to Cd sensitivity, but enhanced Cd root-to-shoot transport, so that increased shoot Cd accumulation. This study provided a possibility to improve phytoextraction efficiency of heavy metal through gene engineering.

Beclin-1-mediated Autophagy Protects Against Cadmium-activated Apoptosis via the Fas/FasL Pathway in Primary Rat Proximal Tubular Cell Culture

The Fas/FasL signaling pathway is one of the primary apoptosis pathways, but the involvement and regulatory mechanism of this pathway by autophagy remain unclear. Here we demonstrated that cadmium (Cd) activated the Fas/FasL apoptosis pathway in rat proximal tubular (rPT) cells; this was accompanied by simultaneous activation of autophagy resulted in reduced apoptosis. In this model, we induced autophagy through RAPA and further demonstrated that autophagy protects against activation of Fas/FasL signaling and apoptosis. The antiapoptotic effect of autophagy was blocked by 3-MA, an autophagy inhibitor. The interactions between Beclin-1 and Fas, FasL, FADD, caspase-8 and BID/tBID were relatively weak, with the exception of cleaved caspase-8, indicated that minimal interactions between these proteins and Beclin-1 are involved in maintaining the balance of autophagy and apoptosis. Beclin-1 precipitated with cleaved caspase-8 in a dose-dependent mannter, and the expression was increased by siRNA against Beclin-1. These data suggested that Beclin-1-mediated autophagy impairs the expression and function of cleaved caspase-8 to protect against Cd-induced activation of apopotosis through Fas/FasL signaling pathway.