Glutathione S-transferases T1 null genotype is associated with susceptibility to aristolochic acid nephropathy

A case-control study and systematic review of the association between glutathione S-transferase genes and chronic kidney disease

Background

GSTM1 deletion was reported to be associated with CKD progression in cohort studies. However, the results of case‒control studies were conflicting. The association between GST genes and CKD progression needs to be studied in China. Therefore, we conducted this case‒control study and systematic review for Southwest China to outline the association between GST genes and CKD.

Methods

CKD patients and healthy controls were enrolled from June 1, 2022 to 1 August 2022. Reported case‒control studies were identified by searching databases until 1 September 2022 for meta-analysis.

Results

Significant associations were found between deletions of GSTM1 and GSTT1 and CKD risk (all P < 0.01) but not in GSTP1 rs1695 (all P > 0.05) in Southwest China. Then, we conducted a meta-analysis on 30 studies and found positive associations between deletions of GSTM1 and GSTT1 and CKD risk (all P < 0.01) but failed to find associations in GSTP1 rs1695 (all P > 0.05). Stratification analysis for ethnicity only showed a significant association in Southern Asia (P < 0.05) but not in Eastern Asia or other populations. This was different from our case‒control results. The current evidence was influenced by study quality and PCR method but not by control selection. Given the different stages of CKD patients, a subanalysis of disease stages was performed, and the results remained positive. Interestingly, we found no significant associations between DM-CKD and GST genes, which should be interpreted with caution.

Conclusion

We found that GSTM1 and GSTT1 null genotypes were risk factors for CKD in China. The results of the meta-analysis were somewhat different from our results. We considered that antioxidant therapy might be useful for the treatment of these patients.

Experimental Aristolochic Acid Nephropathy: A Relevant Model to Study AKI-to-CKD Transition

Aristolochic acid nephropathy (AAN) is a progressive tubulointerstitial nephritis caused by the intake of aristolochic acids (AA) contained in Chinese herbal remedies or contaminated food. AAN is characterized by tubular atrophy and interstitial fibrosis, characterizing advanced kidney disease. It is established that sustained or recurrent acute kidney injury (AKI) episodes contribute to the progression of CKD. Therefore, the study of underlying mechanisms of AA-induced nephrotoxicity could be useful in understanding the complex AKI-to-CKD transition. We developed a translational approach of AKI-to-CKD transition by reproducing human AAN in rodent models. Indeed, in such models, an early phase of acute tubular necrosis was rapidly followed by a massive interstitial recruitment of activated monocytes/macrophages followed by cytotoxic T lymphocytes, resulting in a transient AKI episode. A later chronic phase was then observed with progressive tubular atrophy related to dedifferentiation and necrosis of tubular epithelial cells. The accumulation of vimentin and αSMA-positive cells expressing TGFβ in interstitial areas suggested an increase in resident fibroblasts and their activation into myofibroblasts resulting in collagen deposition and CKD. In addition, we identified 4 major actors in the AKI-to-CKD transition: (1) the tubular epithelial cells, (2) the endothelial cells of the interstitial capillary network, (3) the inflammatory infiltrate, and (4) the myofibroblasts. This review provides the most comprehensive and informative data we were able to collect and examines the pending questions.

Drug-Related Carcinogenesis: Risk Factors and Approaches for Its Prevention

The review summarizes the data on the role of metabolic and repair systems in the mechanisms of therapy-related carcinogenesis and the effect of their polymorphism on the cancer development risk. The carcinogenic activity of different types of drugs, from the anticancer agents to analgesics, antipyretics, immunomodulators, hormones, natural remedies, and non-cancer drugs, is described. Possible approaches for the prevention of drug-related cancer induction at the initiation and promotion stages are discussed.

The pharmacogenetics of natural products: A pharmacokinetic and pharmacodynamic perspective

Natural products have represented attractive alternatives for disease prevention and treatment over the course of human history and have contributed to the development of modern drugs. These natural products possess beneficial efficacies as well as adverse efffects, which vary largely among individuals because of genetic variations in their pharmacokinetics and pharmacodynamics. As with other synthetic chemical drugs, the dosing of natural products can be optimized to improve efficacy and reduce toxicity according to the pharmacogenetic properties. With the emergence and development of pharmacogenomics, it is possible to discover and identify the targets/mechanisms of pharmacological effects and therapeutic responses of natural products effectively and efficiently on the whole genome level. This review covers the effects of genetic variations in drug metabolizing enzymes, drug transporters, and direct and indirect interactions with the pharmacological targets/pathways on the individual response to natural products, and provides suggestions on dosing regimen adjustments of natural products based on their pharmacokinetic and pharmacogenetic paratmeters. Finally, we provide our viewpoints on the importance and necessity of pharmacogenetic and pharmacogenomic research of natural products in natural medicine's rational development and clinical application of precision medicine.

Hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function

Loss of brain glutathione has been associated with cognitive decline and neuronal death during aging and neurodegenerative diseases. However, whether decreased glutathione precedes or follows neuronal dysfunction has not been unambiguously elucidated. Previous attempts to address this issue were approached by fully eliminating glutathione, a strategy causing abrupt lethality or premature neuronal death that led to multiple interpretations. To overcome this drawback, here we aimed to moderately decrease glutathione content by genetically knocking down the rate-limiting enzyme of glutathione biosynthesis in mouse neurons in vivo. Biochemical and morphological analyses of the brain revealed a modest glutathione decrease and redox stress throughout the hippocampus, although neuronal dendrite disruption and glial activation was confined to the hippocampal CA1 layer. Furthermore, the behavioral characterization exhibited signs consistent with cognitive impairment. These results indicate that the hippocampal neurons require a large pool of glutathione to sustain dendrite integrity and cognitive function.

DNA Adducts Formed by Aristolochic Acid Are Unique Biomarkers of Exposure and Explain the Initiation Phase of Upper Urothelial Cancer

Aristolochic acid (AA) is a plant alkaloid that causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN), unique renal diseases frequently associated with upper urothelial cancer (UUC). This review summarizes the significance of AA-derived DNA adducts in the aetiology of UUC leading to specific A:T to T:A transversion mutations (mutational signature) in AAN/BEN-associated tumours, which are otherwise rare in individuals with UCC not exposed to AA. Therefore, such DNA damage produced by AA-DNA adducts is one rare example of the direct association of exposure and cancer development (UUC) in humans, confirming that the covalent binding of carcinogens to DNA is causally related to tumourigenesis. Although aristolochic acid I (AAI), the major component of the natural plant extract AA, might directly cause interstitial nephropathy, enzymatic activation of AAI to reactive intermediates capable of binding to DNA is a necessary step leading to the formation of AA-DNA adducts and subsequently AA-induced malignant transformation. Therefore, AA-DNA adducts can not only be utilized as biomarkers for the assessment of AA exposure and markers of AA-induced UUC, but also be used for the mechanistic evaluation of its enzymatic activation and detoxification. Differences in AA metabolism might be one of the reasons for an individual’s susceptibility in the multi-step process of AA carcinogenesis and studying associations between activities and/or polymorphisms of the enzymes metabolising AA is an important determinant to identify individuals having a high risk of developing AA-mediated UUC.

Balkan endemic nephropathy: an update on its aetiology

Balkan endemic nephropathy (BEN) is a unique, chronic renal disease frequently associated with upper urothelial cancer (UUC). It only affects residents of specific farming villages located along tributaries of the Danube River in Bosnia-Herzegovina, Croatia, Macedonia, Serbia, Bulgaria, and Romania where it is estimated that ~100,000 individuals are at risk of BEN, while ~25,000 have the disease. This review summarises current findings on the aetiology of BEN. Over the last 50 years, several hypotheses on the cause of BEN have been formulated, including mycotoxins, heavy metals, viruses, and trace-element insufficiencies. However, recent molecular epidemiological studies provide a strong case that chronic dietary exposure to aristolochic acid (AA) a principal component of Aristolochia clematitis which grows as a weed in the wheat fields of the endemic regions is the cause of BEN and associated UUC. One of the still enigmatic features of BEN that need to be resolved is why the prevalence of BEN is only 3-7 %. This suggests that individual genetic susceptibilities to AA exist in humans. In fact dietary ingestion of AA along with individual genetic susceptibility provides a scenario that plausibly can explain all the peculiarities of BEN such as geographical distribution and high risk of urothelial cancer. For the countries harbouring BEN implementing public health measures to avoid AA exposure is of the utmost importance because this seems to be the best way to eradicate this once mysterious disease to which the residents of BEN villages have been completely and utterly at mercy for so long.

Lynch syndrome and exposure to aristolochic acid in upper-tract urothelial carcinoma: its clinical impact?

The purpose of the current review was to describe the clinical risk for Lynch syndrome (LS) after exposure to aristolochic acid (AA) in cases of upper urinary-tract urothelial carcinoma (UTUC). A systematic review of the scientific literature was performed using the Medline database (National Library of Medicine, PubMed) using the following keywords: epidemiology, risk factor, AA, Balkan nephropathy (BNe), LS, hereditary cancer, hereditary non-polyposis colorectal cancer (HNPCC), mismatch repair genes, urothelial carcinomas, upper urinary tract, renal pelvis, ureter, Amsterdam criteria, genetic counselling, mismatch repair genes, genetic instability, microsatellite, and Bethesda guidelines. LS is a specific risk for UTUC, which is the third most frequent cancer (in its tumor spectrum) after colon and uterine lesions. Mutation of the MSH2 gene is the most commonly described cause of UTUC in LS. Diagnosis is based on clinical suspicion and is guided by Bethesda and Amsterdam criteria. It is secondarily confirmed by immunohistochemical analyses of the tumor and a search for gene mutations. The presence of LS in patients with UTUC is a favorable prognosis factor for survival during follow-ups. AA is a specific environmental risk factor for UTUC and tubulo-interstitial nephropathy. It has been involved in the development of nephropathies in link with the Balkan disease and intake of Chinese herbal medicine. More broadly, the use of traditional plant medicines from the genus Aristolochia has created worldwide public-health concerns. UTUCs share common risk factors with other urothelial carcinomas such as tobacco or occupational exposure. However, these tumors have also specific risk factors such as AA exposure and LS that clinicians should be aware of because of their clinical implication in further management and follow-up.

Aristolochic acid I is a substrate of BCRP but not P-glycoprotein or MRP2

ETHNOPHARMACOLOGICAL RELEVANCE

Aristolochic acid nephropathy is a severe kidney disease caused by the administration of aristolochic acid, which is widely existed in plants of the Aristolochiaceae family. Aristolochic acid I (AAI) is the main toxic component in aristolochic acid.

AIM OF THE STUDY

The roles of intestinal efflux drug transporters in the transport of AAI are unclear. This study investigates the interaction between AAI and main intestinal efflux transporters.

MATERIALS AND METHODS

Firstly, bidirectional transport of AAI in Caco-2 cell monolayers was investigated. Then, MDCK-MDR1 (gene of P-glycoprotein (P-gp)), MDCK-MRP2 and LLC-PK1-BCRP cell lines were used for further investigation.

RESULTS

In this study, we observed that the efflux ratio of AAI in Caco-2 cell monolayers was 5.8, which indicated that efflux transporters might be involved in the transport of AAI. AAI did not inhibit Rho123 efflux by P-gp and calcein efflux by MRP2, and intracellular accumulation of AAI in P-gp or MRP2 overexpressing cells was not different from their parental cells. These results indicated that AAI was not a substrate of P-gp or MRP2. In contrast, intracellular accumulation of AAI in LLC-PK1-BCRP cells was significantly lower than in their parental cells. The presence of GF120918, a BCRP inhibitor, significantly increased AAI accumulation in BCRP overexpressing cells but not in their parental cells. In addition, bidirectional transport assay of AAI in LLC-PK1-BCRP monolayers showed that the net efflux ratios of AAI were 13.8, 8.0 and 7.0 at 20, 40 and 80 µM AAI, respectively, and decreased to 3.0, 1.9 and 2.0 by the addition of 10 µM GF120918.

CONCLUSIONS

These results indicated that AAI was a substrate of BCRP but not P-gp or MRP2.

Distributions of the GSTM1 and GSTT1 null genotypes worldwide are characterized by latitudinal clines

BACKGROUND

Deletion types of genetic variants of glutathione S-transferase (GST) M1 and T1, the GSTM1 null and GSTT1 null which are risk factors for certain cancers, have been ubiquitously found in human populations but their worldwide distribution pattern is unclear.

MATERIALS AND METHODS

To perform a meta-analysis, a systematic search for the literature on GSTM1 and GSTT1 null genotypes was done to identify 63 reports for 81 human populations. Relationships between the GSTM1 and GSTT1 null genotype frequencies and the absolute latitude of 81 populations were tested by Spearman's rank correlation coefficient.

RESULTS

A significant positive correlation was detected between the GSTM1 null genotype frequency and the absolute latitude (r=0.28, p-value <0.05), whereas the GSTT1 null genotype frequency and absolute latitude showed a significant negative correlation (r= -0.41 p-value <0.01). There was no correlation between the frequencies of GSTM1 and GSTT1 null genotype in each population (r= -0.029, p-value=0.80).

CONCLUSIONS

Latitudinal clines of the distribution of the GSTM1 and GSTT1 null genotypes may be attributed to the result of gene-environmental adaptation. No functional compensation between GSTM1 and GSTT1 was suggested by the lack of correlation between the null frequencies for GSTM1 and GSTT1.

The effect of aristolochic acid I on expression of NAD(P)H:quinone oxidoreductase in mice and rats--a comparative study

Aristolochic acid is the cause of aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN) and their associated urothelial malignancies. Using Western blotting, we investigated the expression of

NAD(P)H

quinone oxidoreductase (NQO1), the most efficient cytosolic enzyme that reductively activates aristolochic acid I (AAI) in mice and rats. In addition, the effect of AAI on the expression of the NQO1 protein and its enzymatic activity in these experimental animal models was examined. We found that NQO1 protein levels in cytosolic fractions isolated from liver, kidney and lung of mice differed from those expressed in these organs of rats. In mice, the highest levels of NQO1 protein and NQO1 activity were found in the kidney, followed by lung and liver. In contrast, the NQO1 protein levels and enzyme activity were lowest in rat-kidney cytosol, whereas the highest amounts of NQO1 protein and activity were found in lung cytosols, followed by those of liver. NQO1 protein and enzyme activity were induced in liver and kidney of AAI-pretreated mice compared with those of untreated mice. NQO1 protein and enzyme activity were also induced in rat kidney by AAI. Furthermore, the increase in hepatic and renal NQO1 enzyme activity was associated with AAI bio-activation and elevated AAI-DNA adduct levels were found in ex vivo incubations of cytosolic fractions with DNA and AAI. In conclusion, our results indicate that AAI can increase its own metabolic activation by inducing NQO1, thereby enhancing its own genotoxic potential.

Knockout and humanized mice as suitable tools to identify enzymes metabolizing the human carcinogen aristolochic acid

1. Aristolochic acid I (AAI) is the predominant component in plant extract of Aristolochia genus that is involved in development of aristolochic acid nephropathy, Balkan endemic nephropathy and urothelial cancer. The diseases do not develop in all individuals exposed to AAI and patients exhibit different clinical outcomes. Differences in the activities of enzymes catalyzing the metabolism of AAI might be one of the reasons for this individual susceptibility. 2. Understanding which human enzymes are involved in reductive activation of AAI generating AAI-DNA adducts, and/or its detoxication to the O-demethylated metabolite, aristolochic acid Ia (AAIa), is necessary in the assessment of the susceptibility to this compound. 3. This review summarizes the results of the latest studies utilizing genetically engineered mouse models to identify which human and rodent enzymes catalyze the reductive activation of AAI to AAI-DNA adducts and its oxidative detoxication to AAIa in vivo. 4. The use of hepatic cytochrome P450 (Cyp) reductase null (HRN) mice, in which NADPH:Cyp oxidoreductase (Por) is deleted in hepatocytes, Cyp1a1((-/-)), Cyp1a2((-/-)) single-knockout, Cyp1a1/1a2((-/-)) double-knockout and CYP1A-humanized mice revealed that mouse and human CYP1A1 and 1A2, besides mouse

NAD(P)H

quinone oxidoreductase, were involved in the activation of AAI but CYP1A1 and 1A2 also oxidatively detoxified AAI.

Acute kidney injury induced by aristolochic acid in patients with primary glomerular nephritis

BACKGROUND

Acute kidney injury induced by aristolochic acid (AA) might occur in patients with chronic glomerular nephritis (CGN). In this study, the clinical and pathological features of patients with acute aristolochic acid nephropathy (AAN) superimposing CGN (AAN-CGN) were investigated.

METHODS

Eighteen patients diagnosed as acute AAN were included in this retrospective study, from January 2001 to December 2009. According to the pre-existing CGN, 13 patients were identified as the AAN-CGN group, and 5 isolated AAN patients as the control group. Clinical and pathological features were compared between the two groups.

RESULTS

In the AAN-CGN group, six patients complained with gastrointestinal symptoms, such as nausea, vomiting, or loss of appetite. The rest of seven cases were asymptomatic or minimally uncomfortable, who were found with elevated serum creatinine (Scr) in the follow up of CGN. Compared with the control group, the patients in AAN-CGN group had higher levels of serum uric acid, urine n-acetyl-β-d-glucosaminidase, and urine protein excretion (366.2 ± 122.8 vs. 218.0 ± 125.8 μmol/L, p = 0.037; 9.74 ± 4.4 vs. 1.38 ± 1.01 g/d, p = 0.001; 61.2 ± 21.9 vs. 27.4 ± 15.8 μ/g ċ cr, p = 0.007, respectively). In addition to, the AAN-CGN patients had an absolutely prominent percentage of macromolecule substance in the urine protein electrophoresis (25.0 ± 6.32 vs. 15.8 ± 7.8%, p = 0.029). The occurrence of hypokalemia and excretion of aminoaciduria were lower than that in the control group. Pathologically, 84.6% of patients were found with tubular brush border dropping, 30.8% with naked tubular basement membrane, and 15.4% with different stages of vascular lesion. There were no statistical differences in the above-mentioned pathological parameters between the two groups. In the follow-up, 10 patients with AAN-CGN recovered with normal Scr, accounting for 76.9%, which was better than the recovery in the control group.

CONCLUSION

Patients with acute AAN-CGN manifested with a great mass of urine protein excretion, low incidence of hypokalemia and aminoaciduria, however, the tubular-interstitial lesions were similar to the isolated AAN.