Heavy metal imaging in fibrotic human kidney tissue using the synchrotron X-ray fluorescence microprobe

Mercuric Chloride Induced Nephrotoxicity: Ameliorative Effect of Carica papaya Leaves Confirmed by Histopathology, Immunohistochemistry, and Gene Expression Studies

The present study analyzes the efficacy of the ethanolic extract of C. papaya leaves (ECP) against HgCl₂-induced nephrotoxicity. The effects on the biochemical and percentage of body and organ weight against HgCl₂-induced nephrotoxicity in female Wistar rats were studied. Wistar rats were divided into five groups with six animals in each group: control, HgCl₂ (2.5 mg/kg b.w.), N-acetylcysteine (NAC 180 mg/kg) + HgCl₂, ECP (300 mg/kg b.w.) + HgCl₂, and ECP (600 mg/kg) + HgCl₂ groups. After 28 days of study, animals were sacrificed on the 29th day to harvest the blood and kidneys for further analysis. The effect ECP was analyzed by immunohistochemistry (NGAL) and real-time PCR (KIM-1 and NGAL mRNA) in HgCl₂-induced nephrotoxicity. The results revealed that the HgCl₂ group showed prominent damage in the proximal tubules and glomerulus of nephrons and enormous expression of NGAL in immunohistochemistry and KIM-1 and NGAL in real-time PCR compared to the control group. The simultaneous pretreatment with NAC (180 mg/kg) and ECP (600 and 300 mg/kg) reduced renal damage and expression of NGAL in immunohistochemistry and KIM-1 and NGAL gene in real-time PCR. This study attests to the nephroprotective effect of ECP against HgCl₂-induced toxicity.

Cadmium-Induced Proteinuria: Mechanistic Insights from Dose-Effect Analyses

Cadmium (Cd) is a toxic metal that accumulates in kidneys, especially in the proximal tubular epithelial cells, where virtually all proteins in the glomerular ultrafiltrate are reabsorbed. Here, we analyzed archived data on the estimated glomerular filtration rate (eGFR) and excretion rates of Cd (E_Cd), total protein (E_Prot), albumin (E_alb), β₂-microglobulin (E_β2M), and α1-microglobulin (E_α1M), which were recorded for residents of a Cd contamination area and a low-exposure control area of Thailand. Excretion of Cd and all proteins were normalized to creatinine clearance (C_cr) as E_Cd/C_cr and E_Prot/C_cr to correct for differences among subjects in the number of surviving nephrons. Low eGFR was defined as eGFR ≤ 60 mL/min/1.73 m², while proteinuria was indicted by E_Pro/C_cr ≥ 20 mg/L of filtrate. E_Prot/C_cr varied directly with E_Cd/C_cr (β = 0.263, p < 0.001) and age (β = 0.252, p < 0.001). In contrast, eGFR values were inversely associated with E_Cd/C_cr (β = -0.266, p < 0.001) and age (β = -0.558, p < 0.001). At E_Cd/C_cr > 8.28 ng/L of filtrate, the prevalence odds ratios for proteinuria and low eGFR were increased 4.6- and 5.1-fold, respectively (p < 0.001 for both parameters). Thus, the eGFR and tubular protein retrieval were both simultaneously diminished by Cd exposure. Of interest, E_Cd/C_cr was more closely correlated with E_Prot/C_cr (r = 0.507), E_β2M (r = 0.430), and E_α1M/C_cr (r = 0.364) than with E_Alb/C_cr (r = 0.152). These data suggest that Cd may differentially reduce the ability of tubular epithelial cells to reclaim proteins, resulting in preferential reabsorption of albumin.

Kidney Cadmium Concentrations in an Urban Sri Lankan Population: an Autopsy Study

Contamination and bioaccumulation of toxic heavy metals in our geo-environment is a growing public health concern. Human biomonitoring is an essential step in assessing the population risk of chronic exposure to environmental contaminants. Whole kidneys collected from a cohort of 92 deceased individuals undergoing forensic autopsies in Colombo, Sri Lanka, were analysed for cadmium (Cd) bioaccumulation using ICP-MS. Mean age of the population was 55.4 ± 15.4 years. Mean and median renal Cd concentrations of the total population were 4.38 and 2.60 μg g^-1 w/w, respectively, which were below estimated toxic ranges. Males accumulated higher levels of Cd than females (p = 0.377). Cd concentrations were higher in the < 60 age group than the > 60 age group (p = 0.92), while the highest levels were reported in 51-60 age group. However, no significant correlation was found between renal Cd concentration and age (Ʈ_b = - 0.005, p = 0.94). Individuals who smoked, chewed betel or consumed alcohol were found to have elevated renal Cd concentrations in comparison to those who did not use these substances. This is the largest autopsy study on renal Cd bioaccumulation in Sri Lanka, and the findings do not indicate a high exposure risk to environmental Cd contamination at present.

Quercetin alleviates cadmium chloride-induced renal damage in rats by suppressing endoplasmic reticulum stress through SIRT1-dependent deacetylation of Xbp-1s and eIF2α

Endoplasmic reticulum (ER) stress plays a key role in cadmium chloride (CdCl2)-induced nephrotoxicity. Sirtuin-1 (SIRT1) is a potent inhibitor of ER stress. In this study, we examined whether the protective effect of quercetin (QUR) against CdCl₂-induced nephrotoxicity in rats involved modulation of SIRT1 and/or ER stress. Adult male rats were divided into five groups (n = 8, each) and treated for eight weeks as follows: control, control + QUR, CdCl₂, CdCl₂ + QUR, and CdCl₂ + QUR + EX-527 (a SIRT1 inhibitor). Treatment of rats with QUR preserved the glomerulus and tubule structure, attenuated interstitial fibrosis, increased creatinine excretion, and reduced urinary levels of albumin, N-acetyl-β-D-glucosaminidase, and β2-microglobulin in CdCl₂-treated rats. Concomitantly, QUR increased renal levels of Bcl-2, reduced mRNA levels of CHOP, and protein levels of Bax, caspase-3, and cleaved caspase-3, but failed to reduce the mRNA levels of GRP78, PERK, eIf2α, ATF-6, and xbp-1. QUR also reduced the renal levels of reactive oxygen species, tumour necrosis factor, and interleukin-6 and the nuclear activity of NF-κB in the control and CdCl₂-treated rats but increased the nuclear activity of Nrf2 and levels of glutathione and manganese superoxide dismutase. Additionally, QUR increased the total levels and nuclear activity of SIRT1 and reduced the acetylation of eIf2α and xbp-1. The nephroprotective effects of QUR were abrogated by treatment with EX-527. Thus, QUR ameliorated CdCl₂-induced nephrotoxicity through antioxidant and anti-inflammatory effects and suppressed ER stress mediated by the upregulation or activation of SIRT1-induced deacetylation of Nrf2, NF-κB p65, eIF2α, and xbp-1.

Renal bioaccumulation of trace elements in urban and rural Sri Lankan populations: A preliminary study based on post mortem tissue analysis

INTRODUCTION

Environmental pollution, especially by toxic trace elements, is a global health concern. Heavy metals such as Cadmium (Cd), Arsenic (As) and Lead (Pb) are associated with numerous disorders and are considered by some as an aetiological factor for the Chronic Kidney Disease (CKDu1) epidemic in Sri Lanka. This study explores patterns of bioaccumulation of six trace elements in kidneys obtained during forensic autopsies from urban and rural regions in Sri Lanka.

METHODS

Kidney samples obtained from one urban district (n = 13) and three rural districts (n = 18) were lyophilized, microwave digested and profiled by ICP-MS techniques.

RESULTS AND DISCUSSION

The mean age of the sampled population was 47.9 ± 11.3 yrs. Median (IQR) for Cd, As, Pb, Cr, Zn and Se were, 14.67(8.04-22.47) μg/g, 0.44(0.29-0.56) μg/g, 0.11(0.07-0.30) μg/g, 0.15(0.1096-0.3274), 25.55(17.24-39.35) μg/g and 0.52(0.37-0.84) μg/g, respectively. Cd, Zn and Se levels were significantly higher (p < 0.05) among the urban samples compared to that of the rural group. Zn and Se levels were higher among younger age groups. As, Pb and Cr did not show any significant differences between the two cohorts nor any correlations with age.

CONCLUSION

This population-specific baseline study provides an insight into the differences in exposure to toxic trace elements and essential elements between urban and rural populations. Residents in CKDu affected rural districts did not appear to be at risk of toxic heavy metal exposure, however their renal bioaccumulation of nephroprotective essential elements was lower than urban residents.