Variation of different metabolites and heavy metals in Oryza sativa L., related to chronic kidney disease of unknown etiology in Sri Lanka

Relationship between heavy metal concentrations and Chronic kidney disease in population of Hoveyzeh cohort study: A cross-sectional study in Iran

BACKGROUND

Chronic kidney disease (CKD) is a multifactorial disease whose prevalence is increasing worldwide. CKD affects 700 million to 1 billion people worldwide, with a prevalence of 9.1% to 13.4%. In Iran, the reported prevalence of CKD is 15.14%, even higher than the global prevalence. Some studies introduced heavy metals as possible risk factors of CKD. We conducted the first study in Iran to examine the relationship between 10 selected urinary heavy metals and CKD in the Hovayzeh cohort study population.

METHODS

In this cross-sectional study, urine samples were collected from two groups of ca ses (suffering from CKD) and controls (without CKD) with equal size (47 people each). Analysis of the 10 sellected heavy metals in the samples was conducted using inductively coupled plasma emission spectroscopy. Basic Information was obtained from the Howayizeh Cohort Study Center. The data was analyzed using SPSS-26 and Excel-2016 software.

RESULTS

There were no significant differences between urinary heavy metal concentrations of case and control groups (P < 0.05). While, the concentration of As, Cr, Cu, Mn, and Ni exceeded the reference limits of Germany, Canada, England, and Belgium. Se and Cd also surpassed the reference limits of England. After adjusting for confounding variables for each μg/l increase in urinary Cd, Ni, Pb, and Se the OR of CKD increased by 20.2%, 4.8%, 3.1%, and 2.6%, respectively. Although, these relationships were not statistically significant. In addition, two groups of heavy metals had a positive and significant correlation: (1) Se, Zn, As, Cu, and Cr; (2) Pb, Cd, and As; and (3) Cd and Ni.

CONCLUSION

we found no significant relationship between urinary heavy metal and CKD. However, there was significant positive correlation in some of urinary heavy metals may indicate their shared resources. Furthermore, the concentration of most heavy metals in the urine of the participants was higher than the reference limits of these metals in the urine of healthy people from other countries. Thus, the elevated levels of these metals could still pose a risk to human health. Therefore, it is necessary to conduct prospective studies with a larger sample size in this area.

Metabolome evidence of CKDu risks after chronic exposure to simulated Sri Lanka drinking water in zebrafish

It is still a serious public health issue that chronic kidney disease of uncertain etiology (CKDu) in Sri Lanka poses challenges in identification, prevention, and treatment. What environmental factors in drinking water cause kidney damage remains unclear. This study aimed to investigate the risks of various environmental factors that may induce CKDu, including water hardness, fluoride (HF), heavy metals (HM), microcystin-LR (MC-LR), and their combined exposure (HFMM). The research focused on comprehensive metabolome analysis, and correlation with transcriptomic and gut microbiota changes. Results revealed that chronic exposure led to kidney damage and pancreatic toxicity in adult zebrafish. Metabolomics profiling showed significant alterations in biochemical processes, with enriched metabolic pathways of oxidative phosphorylation, folate biosynthesis, arachidonic acid metabolism, FoxO signaling pathway, lysosome, pyruvate metabolism, and purine metabolism. The network analysis revealed significant changes in metabolites associated with renal function and diseases, including 20-Hydroxy-LTE4, PS(18:0/22:2(13Z,16Z)), Neuromedin N, 20-Oxo-Leukotriene E4, and phenol sulfate, which are involved in the fatty acyls and glycerophospholipids class. These metabolites were closely associated with the disrupted gut bacteria of g_ZOR0006, g_Pseudomonas, g_Tsukamurella, g_Cetobacterium, g_Flavobacterium, which belonged to dominant phyla of Firmicutes and Proteobacteria, etc., and differentially expressed genes (DEGs) such as egln3, ca2, jun, slc2a1b, and gls2b in zebrafish. Exploratory omics analyses revealed the shared significantly changed pathways in transcriptome and metabolome like calcium signaling and necroptosis, suggesting potential biomarkers for assessing kidney disease.

Rising of a global silent killer: critical analysis of chronic kidney disease of uncertain aetiology (CKDu) worldwide and mitigation steps

Chronic kidney disease of uncertain aetiology (CKDu) is an advanced version of chronic kidney disease (CKD) which bears a high burden on the world health economy. More than 200 articles were analysed to understand the disease responsible for more than 30,000 deaths per year. CKDu is a non-communicable occupational disease that has a progressive deterioration of the kidney in the absence of CKD risk factors such as hypertension, diabetes and glomerulonephritis, while the diagnosis is only possible at the later stages when kidney function is no longer effective. Published evidence for the existence of CKDu was found for around 35 countries. This is a growing health issue in Asia, Central America, Africa and Middle East with identified hot spots. Despite many research studies over decades, the exact root causes are still uncertain. Six main suspected causative factors are identified. Those are heat stress, strenuous labour, dehydration, use of agrochemicals, exposure to heavy metals and the use of polluted water and agricultural lands. This review summarizes four key areas which are CKDu and its general medical background, worldwide prevalence, suspected causative factors and potential circumventing steps to mitigate against CKDu. The importance of further studies addressing early detection and surveillance methods, contribution of nephrotoxins in environmental health, soil chemistry on transporting nephrotoxins, geological parameters which influence the prevalence of the disease and other related sectors to overcome the mysterious nature is highlighted. Mitigation steps to lessen the burden of CKDu are also identified.

Increasing soil Mn abundance promotes the dissolution and oxidation of Cr(III) and increases the accumulation of Cr in rice grains

Hexavalent chromium (Cr(VI)) is more readily taken up by plants than trivalent chromium (Cr(III)) due to its similar chemical structure to phosphate and sulfate. In paddy soils, Cr(VI) of natural origin are mainly produced from Cr(III) oxidized by O2 and Mn(III/IV) oxides, which are affected by rice radial oxygen loss (ROL) and Mn(II)-oxidizing microorganisms (MOM). However, little is known about the effect of ROL and Mn abundance on rice Cr uptake. Here, we investigated the effects on Cr(VI) generation and the subsequent Cr uptake and accumulation with the involvement of two rice cultivars with distinct ROL capacities by increasing soil Mn abundance. Results showed that Mn(II) addition to the soil led to more Cr(III) being released into the pore water, and the dissolved Cr(III) was oxidized to Cr(VI) by ROL and biogenic Mn(III/IV) oxides. The concentration of Cr(VI) in soil and pore water increased linearly with the addition of Mn(II) doses. Mn(II) addition promoted the root-to-shoot translocation and grain accumulation of Cr derived mainly from newly generated Cr(VI) in the soil. These results emphasize that rice ROL and MOM promote the oxidative dissolution of Cr(III) at a high level of soil Mn, resulting in more Cr accumulation in rice grains and increasing dietary Cr exposure risks.

Physiological and transcriptomic analysis reveal the regulatory mechanism underlying grain quality improvement induced by rice ratooning

BACKGROUND

Ratoon rice cropping has been introduced for increased rice production in southern China and, as a result, has been becoming increasingly popular. However, only a few studies have addressed the regulatory mechanism underlying grain quality improvement induced by rice ratooning.

RESULTS

In this study, parameters of rice quality, including head rice yield, chalky grain percentage, grain chalkiness degree, hardness and taste value, were shown to be much improved in the ratooning season rice as compared to its counterparts main and late cropping season rice, indicating that such an improvement was irrespective of seasonal effects. In addition, the nutritional components of grains varied greatly between main-cropping season rice, ratooning season rice and late-cropping season rice and displayed a significant correlation with rice quality. Finally, the regulatory mechanism underlying rice quality improvement revealed that gibberellin-dominated regulation and plant hormone signal transduction jointly contributed to a decrease in formation of chalky grains.

CONCLUSION

This work improves our knowledge on rice quality improvement under rice ratooning, particularly on the regulatory mechanism of plant hormones. © 2022 Society of Chemical Industry.

Nuclear factor-kappaB mediates the survival of rat kidney cells after cadmium exposure via promoting autophagy and inhibiting apoptosis

Cadmium (Cd) is a heavy metal pollutant in the environment, and the kidney is one of the target organs after Cd exposure. Previous studies have shown that apoptosis and autophagy disorders are the main mechanisms of Cd-induced nephrotoxicity in rats. As a transcription factor that balances cell survival and death, nuclear factor-kappaB (NF-κB) protein plays dual regulatory effects on apoptosis and autophagy in multiple renal diseases. However, the regulatory mechanisms of NF-κB in Cd-induced kidney injury remain unclear. Therefore, the normal rat kidney cell line (NRK-52E cells) was applied to investigate the above questions in this study. Here, we found that Cd promotes the nuclear translocation and activation of NF-κB in a concentration-dependent manner, and activated NF-κB mediates NRK-52E cells survival after Cd exposure. Next, our study elaborated the mechanisms of NF-κB in antagonizing Cd-induced renal cytotoxicity. Inhibition of NF-κB by inhibitor BAY 11-7082 (BAY) and NF-κB p65 siRNA (siNF-κB p65) exacerbate Cd-induced apoptosis and autophagy inhibition, and then aggravate Cd-induced NRK-52E cells injury. Activation of NF-κB by activator phorbol-12-myristate-13-acetate (PMA) alleviates Cd-induced apoptosis and autophagy inhibition, and then attenuates Cd-induced NRK-52E cells injury. In conclusion, Cd exposure promotes the activation of NF-κB, and activated NF-κB mediates the survival of NRK-52E cells after Cd exposure via promoting autophagy and inhibiting apoptosis.

Equilibrium Isotherms, Kinetics, and Thermodynamic Mechanisms of a Novel Polyacrylamide-Strychnos potatorum Seed-Derived Activated Carbon Composite for Aqueous Hardness Removal

Hardness in water is responsible for both residential and industrial problems. Moreover, drinking hard water is suspected as the main cause of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. The major constituents that are responsible for water hardness are calcium and magnesium ions. In this study, a composite was synthesized using activated carbon of Strychnos potatorum seeds (ACSP) and acrylamide to remove hardness in drinking water. The synthesized composite was characterized using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and scanning electron microscope (SEM). According to this study, the process of removal of hardness depends on the contact time, adsorbent dosage, initial contents, and pH of the solution. The adsorption data were well fitted to the Freundlich isotherm and the pseudo-second-order kinetic models. Furthermore, environmental samples collected from Anuradhapura, Sri Lanka, which is well known for water with high hardness, were treated with an adsorbent, and hardness was reduced effectively. Moreover, the adsorption appeared to be spontaneous in nature. Finally, it can be concluded that this adsorbent can be used as an effective hardness-removing agent.

Comprehensive Groundwater Quality Analysis in Chronic Kidney Disease of Unknown Etiology (CKDu) Prevalence Areas of Sri Lanka to Investigate the Responsible Culprit

Chronic kidney disease of unknown etiology (CKDu) is a serious health problem in Sri Lanka especially among agricultural communities in dry zone since 19th century. In the present study, several water quality parameters were studied in well water samples and only four parameters, namely, hardness, cadmium level, fluoride level, and strontium level have shown a relationship with the CKDu prevalence. Higher percentage of well water samples collected from CKDu prevalent area in both pre and postmonsoon seasons have exceeded the WHO recommended levels of hardness. Further, water samples collected in postmonsoon seasons had significantly higher hardness than the well water samples collected in premonsoon season ( $P<0.05$ ). This may be due to the dissolution of calcium carbonate by water recharge. Moreover, cadmium and fluoride contents have exceeded the recommended levels in high-risk area during the premonsoon period. Furthermore, according to principal component analysis (PCA), four clusters were identified depending on the different levels of fluoride, cadmium, hardness, and strontium contents. The control area (Am) fell in to separate cluster with low contents of fluoride, cadmium, hardness, and strontium than in CKDu prevalent area. Since it has been found that the above species are directly involved in renal damage, it can be concluded that a synergetic effect of cadmium, fluoride, hardness, and strontium in well water may be a main cause for CKDu in Sri Lanka.

Chronic kidney disease of unknown etiology in India: a comparative study with Mesoamerican and Sri Lankan nephropathy

Chronic kidney disease of unknown etiology [CKDu] is a condition characterized by decline in kidney function and is not associated with diabetic nephropathy or hypertensive nephropathy. In this review, we have done a detailed literature analysis on CKDu in India, and then had a comparison with that of Mesoamerica and Sri Lanka. In India, CKDu became the second most common type of CKD after diabetic nephropathy. Silica was seen in the groundwater of both India and Sri Lanka, whereas in Mesoamerica silica exposure through particulate matter was seen among CKDu communities. DDE is a common agrochemical seen in both India and Sri Lanka. The risk factors vary from region to region and it is important to categorize CKDu population based on the risk factors to avoid misinterpretation of the condition as non-CKDu category and to evade further complications. More studies have to be conducted to reveal the detailed pathophysiological mechanisms and its relation with irrational exploitation of environmental resources.

The epigenetic regulator BRD4 is involved in cadmium-triggered inflammatory response in rat kidney

Cadmium (Cd) has been described as a potential inflammatory inducer, while increasing evidence shows that inappropriate inflammation is a contributing factor to kidney injury. Hence, research on Cd-triggered inflammatory response is of great significance for elucidating the mechanism of Cd-induced nephrotoxicity. Bromodomain-containing 4 (BRD4) is an important epigenetic regulator involved in the development of many inflammatory diseases, but its regulatory roles in Cd-triggered inflammatory response remain to be clarified. Here, we found that treatment with Cd in Sprague-Dawley rats (2 mg/kg bw, i.p., 5 consecutive days) and in rat kidney cell line (NRK-52E, 0-10 μM, 12 h) induced the transcription of inflammatory cytokines, which could be reduced by JQ1 (BRD4 inhibitor, 25 mg/kg bw, i.p., 3 consecutive days in vivo; 0.5 μM, 12 h in vitro) or BRD4 small interfering RNA (siRNA, in vitro), suggesting that BRD4 participates in Cd-triggered inflammatory response. Next, our study clarified the roles of BRD4 in Cd-triggered inflammatory response. The inhibition of BRD4 decreased Cd-promoted NF-κB nuclear translocation and activation in vivo and in vitro. Cd increased the acetylation level of RelA K310 and enhanced BRD4 binding to acetylated NF-κB RelA in vivo and in vitro, which were abrogated by inhibiting BRD4. In summary, our study suggests that BRD4 is involved in Cd-triggered transcription of inflammatory cytokines by mediating the activation of NF-κB signaling pathway and increasing itself binding to acetylated NF-κB RelA in rat kidney, therefore, BRD4 could be a potential therapeutic target for Cd-induced renal diseases.