Revealing a Pre-neoplastic Renal Tubular Lesion by p-S6 Protein Immunohistochemistry after Rat Exposure to Aristolochic Acid

Abstract

Aristolochic acid (AA) has, in the last decade, become widely promoted as the cause of the Balkan endemic nephropathy and associated renal or urothelial tumours, although without substantial focal evidence of the quantitative dietary exposure via bread in specific households in hyperendemic villages. Occasional ethnobotanical use of Aristolochia clematitis might be a source of AA, and Pliocene lignite contamination of well-water is also a putative health risk factor. The aim of this study was two-fold: to verify if extracts of A. clematitis and Pliocene, or AA by itself, could induce the development of renal or urothelial tumours, and to test the utility of the ribosomal protein p-S6 to identify preneoplastic transformation. Rats were given extracts of A. clematitis in drinking water or AA I, by gavage. After seven months, renal morphology was studied using conventional haematoxylin and eosin and immunohistochemistry for ribosomal p-S6 protein. Plant extracts (cumulative AA approximately 1.8 g/kg b.w.) were tolerated and caused no gross pathology or renal histopathological change, with only faint diffuse p-S6 protein (except in the papilla) as in controls. Cumulative AA I (150 mg/kg b.w. given over 3 days) was also tolerated for seven months by all recipients, without gross pathology or kidney tumours. However, p-S6 protein over-expression was consistent particularly within the renal papilla. In one case given AA I, intense p-S6 protein staining of a proximal tubule fragment crucially matched the pre-neoplastic histology in an adjacent kidney section. We briefly discuss these findings, which compound uncertainty concerning the cause of the renal or upper urinary tract tumours of the Balkan endemic nephropathy.

Environmental pollutants-dependent molecular pathways and carcinogenesis

“…Previous studies have suggested that environmental factors are able to induce deleterious effects within the cells through the activation of cellular receptors (Mnif et al 2007, Routledge et al 2000). It is important to note that the interactions between most of the environmental pollutants and their receptors are implicated in the regulation of molecular pathways involved in cancer progression, such as proliferation, metabolism of xenobiotics and apoptosis (Burz et al 2009, Duronio and Xiong 2013, Rushmore and Kong 2002. It is known that environmental molecules, such as TCDD, B[a]P, BPA and phthalates, have the ability to interact with the two types of cellular receptors: nuclear and membrane receptors (Delfosse et al 2014, Dong 2006, Wallace andRedinbo 2013).…”

“…Three major classes of membrane receptors exist: 1) the enzyme linked-receptors that lack intrinsic catalytic activity and dimerise after binding with their ligands, in order to activate downstream signal transductions pathways through one or more cytosolic protein-tyrosine kinase (i.e. human growth factor receptors) (Dudek 2007); 2) the channel-linked receptors (also called ligand-gated ion channels) where the ligand binding changes the conformation of the receptor; in this case, specific ions flow through the channel altering the electric potential across the membrane of the target cell (Absalom et al 2004); and 3) the G-protein coupled receptors (GPCRs).…”

“…The present review will highlight the recent research advances regarding carcinogenic mechanisms with the focus on two receptors in mediating environmental pollutants effects: the established nuclear receptor the Aryl hydrocarbon receptor (AhR), known to have a major role in the metabolism of toxic compounds and the promotion of tumours and the emerging membrane receptor G-protein coupled estrogen receptor 1 (GPER1), known to mediate estrogenic activity of environmental xeno-estrogens in different cell types (Filardo 2018, Xue et al 2018).…”

“…It is well known that the environmental molecule B[a]P induces, via AhR, the expression of CYP1A1, which is involved in the biotransformation of B[a]P, a procarcinogen, into B[a]P-diol-epoxide (BPDE), an ultimate mutagen with a strong electrophilic power that allows it to form DNA adducts that cause cytogenetic alterations, DNA breaks, DNA damage and mutations in oncogenes and tumour suppressor genes (Chiang and Tsou 2009, IARC 2012, Morris and Seifter 1992, Rundle et al 2000, Tarantini et al 2011. BPDE was demonstrated to induce K-ras mutations in normal human bronchial epithelial and fibroblast cells; these mutations have also been found in lung tumours of people exposed to the smoke of charcoal combustion during their work (Feng et al 2002, IARC 2010.…”

“…Several studies have highlighted the use of GPER1 as a cancer biomarker. The results of a clinical study showed that the expression of GPER-1 might correlate with clinical and pathological-poor outcome biomarkers, by showing an association with metastasis, human epidermal growth factor receptor 2 (HER2) expression and tumour size (Filardo et al 2006). GPER1 has also been shown to be an important prognostic factor in high-risk endometrial cancer patients with lower survival rates (Smith et al 2007).…”