Renal hypoxia-HIF-PHD-EPO signaling in transition metal nephrotoxicity: friend or foe?

Deciphering the role of circular RNAs in cancer progression under hypoxic conditions

Hypoxia, characterized by reduced oxygen levels, plays a pivotal role in cancer progression, profoundly influencing tumor behavior and therapeutic responses. A hallmark of solid tumors, hypoxia drives significant metabolic adaptations in cancer cells, primarily mediated by hypoxia-inducible factor-1α (HIF-1α), a key transcription factor activated in low-oxygen conditions. This hypoxic environment promotes epithelial-mesenchymal transition (EMT), enhancing cancer cell migration, metastasis, and the development of cancer stem cell-like properties, which contribute to therapy resistance. Moreover, hypoxia modulates the expression of circular RNAs (circRNAs), leading to their accumulation in the tumor microenvironment. These hypoxia-responsive circRNAs regulate gene expression and cellular processes critical for cancer progression, making them promising candidates for diagnostic and prognostic biomarkers in various cancers. This review delves into the intricate interplay between hypoxic circRNAs, microRNAs, and RNA-binding proteins, emphasizing their role as molecular sponges that modulate gene expression and signaling pathways involved in cell proliferation, apoptosis, and metastasis. It also explores the relationship between circRNAs and the tumor microenvironment, particularly how hypoxia influences their expression and functional dynamics. Additionally, the review highlights the potential of circRNAs as diagnostic and prognostic tools, as well as their therapeutic applications in innovative cancer treatments. By consolidating current knowledge, this review underscores the critical role of circRNAs in cancer biology and paves the way for future research aimed at harnessing their unique properties for clinical advancements. Specifically, this review examines the biogenesis, expression patterns, and mechanistic actions of hypoxic circRNAs, focusing on their ability to act as molecular sponges for microRNAs and their interactions with RNA-binding proteins. These interactions impact key signaling pathways related to tumor growth, metastasis, and drug resistance, offering new insights into the complex regulatory networks governed by circRNAs under hypoxic stress.

Investigating the relationship of co-exposure to multiple metals with chronic kidney disease: An integrated perspective from epidemiology and adverse outcome pathways

Systematic studies on the associations between co-exposure to multiple metals and chronic kidney disease (CKD), as well as the underlying mechanisms, remain insufficient. This study aimed to provide a comprehensive perspective on the risk of CKD induced by multiple metal co-exposures through the integration of occupational epidemiology and adverse outcome pathway (AOP). The study participants included 401 male mine workers whose blood metal, β2-microglobulin (β2-MG), and cystatin C (Cys-C) levels were measured. Generalized linear models (GLMs), quantile g-computation models (qgcomp), least absolute shrinkage and selection operator (LASSO), and bayesian kernel machine regression (BKMR) were utilized to identify critical nephrotoxic metals. The mean concentrations of lead, cadmium, mercury, arsenic, and manganese were 191.93, 3.92, 4.66, 3.11, 11.35, and 16.33 µg/L, respectively. GLM, LASSO, qgcomp, and BKMR models consistently identified lead, cadmium, mercury, and arsenic as the primary contributors to kidney toxicity. Based on our epidemiological analysis, we used a computational toxicology method to construct a chemical-genetic-phenotype-disease network (CGPDN) from the Comparative Toxicogenomics Database (CTD), DisGeNET, and GeneCard databases, and further linked key events (KEs) related to kidney toxicity from the AOP-Wiki and PubMed databases. Finally, an AOP framework of multiple metals was constructed by integrating the common molecular initiating events (reactive oxygen species) and KEs (MAPK signaling pathway, oxidative stress, mitochondrial dysfunction, DNA damage, inflammation, hypertension, cell death, and kidney toxicity). This is the first AOP network to elucidate the internal association between multiple metal co-exposures and CKD, providing a crucial basis for the risk assessment of multiple metal co-exposures.

Insoluble HIFa protein aggregates by cadmium disrupt hypoxia-prolyl hydroxylase (PHD)-hypoxia inducible factor (HIFa) signaling in renal epithelial (NRK-52E) and interstitial (FAIK3-5) cells

The kidney is the main organ that senses changes in systemic O2 pressure by hypoxia-PHD-HIFa (HPH) signaling, resulting in adaptive target gene activation, including erythropoietin (EPO). The non-essential transition metal cadmium (Cd) is nephrotoxic and disrupts the renal HPH pathway, which may promote Cd-associated chronic renal disease (CKD). A deeper molecular understanding of Cd interference with renal HPH signaling is missing, and no data with renal cell lines are available. In rat kidney NRK-52E cells, which model the proximal tubule, and murine fibroblastoid atypical interstitial kidney (FAIK3-5) cells, which mimic renal EPO-producing cells, the chemical hypoxia mimetic dimethyloxalylglycine (DMOG; 1 mmol/l) or hypoxia (1% O2) activated HPH signaling. Cd2+ (2.5-20 µmol/l for ≤ 24 h) preferentially induced necrosis (trypan blue uptake) of FAIK3-5 cells at high Cd whereas NRK-52E cells specially developed apoptosis (PARP-1 cleavage) at all Cd concentrations. Cd (12.5 µmol/l) abolished HIFa stabilization and prevented upregulation of target genes (quantitative real-time polymerase chain reaction and immunoblotting) induced by DMOG or hypoxia in both cell lines, which was caused by the formation of insoluble HIFa aggregates. Strikingly, hypoxic preconditioning (1% O2 for 18 h) reduced apoptosis of FAIK3-5 and NRK-52E cells at low Cd concentrations and decreased insoluble HIFa proteins. Hence, drugs mimicking hypoxic preconditioning could reduce CKD induced by chronic low Cd exposure.

Impact of Metal Ions on Cellular Functions: A Focus on Mesenchymal Stem/Stromal Cell Differentiation

Metals play a crucial role in the human body, especially as ions in metalloproteins. Essential metals, such as calcium, iron, and zinc are crucial for various physiological functions, but their interactions within biological networks are complex and not fully understood. Mesenchymal stem/stromal cells (MSCs) are essential for tissue regeneration due to their ability to differentiate into various cell types. This review article addresses the effects of physiological and unphysiological, but not directly toxic, metal ion concentrations, particularly concerning MSCs. Overloading or unbalancing of metal ion concentrations can significantly impair the function and differentiation capacity of MSCs. In addition, excessive or unbalanced metal ion concentrations can lead to oxidative stress, which can affect viability or inflammation. Data on the effects of metal ions on MSC differentiation are limited and often contradictory. Future research should, therefore, aim to clarify the mechanisms by which metal ions affect MSC differentiation, focusing on aspects such as metal ion interactions, ion concentrations, exposure duration, and other environmental conditions. Understanding these interactions could ultimately improve the design of biomaterials and implants to promote MSC-mediated tissue regeneration. It could also lead to the development of innovative therapeutic strategies in regenerative medicine.

Epigenotoxicity: Decoding the epigenetic imprints of genotoxic agents and their implications for regulatory genetic toxicology

Regulatory genetic toxicology focuses on DNA damage and subsequent gene mutations. However, genotoxic agents can also affect epigenetic marks, and incorporation of epigenetic data into the regulatory framework may thus enhance the accuracy of risk assessment. Additionally, epigenetic alterations may identify non-genotoxic carcinogens that are not captured with the current battery of tests. Epigenetic alterations could also explain long-term consequences and potential transgenerational effects in the absence of DNA mutations. Therefore, at the 2022 International Workshops on Genotoxicity Testing (IWGT) in Ottawa (Ontario, Canada), an expert workgroup explored whether including epigenetic endpoints would improve regulatory genetic toxicology. Here we summarize the presentations and the discussions on technical advancements in assessing epigenetics, how the assessment of epigenetics can enhance strategies for detecting genotoxic and non-genotoxic carcinogens and the correlation between epigenetic alterations with other relevant apical endpoints.

Modified Zhenwu Tang delays chronic renal failure progression by modulating oxidative stress and hypoxic responses in renal proximal tubular epithelial cells

Background

Tubulointerstitial fibrosis (TIF) is a critical pathological feature of chronic renal failure (CRF), with oxidative stress (OS) and hypoxic responses in renal proximal tubular epithelial cells playing pivotal roles in disease progression. This study explores the effects of Modified Zhenwu Tang (MZWT) on these processes, aiming to uncover its potential mechanisms in slowing CRF progression.

Methods

We used adenine (Ade) to induce CRF in rats, which were then treated with benazepril hydrochloride (Lotensin) and MZWT for 8 weeks. Assessments included liver and renal function, electrolytes, blood lipids, renal tissue pathology, OS levels, the hypoxia-inducible factor (HIF) pathway, inflammatory markers, and other relevant indicators. In vitro, human renal cortical proximal tubular epithelial cells were subjected to hypoxia and lipopolysaccharide for 72 h, with concurrent treatment using MZWT, FM19G11, and N-acetyl-l-cysteine. Measurements taken included reactive oxygen species (ROS), HIF pathway activity, inflammatory markers, and other relevant indicators.

Results

Ade treatment induced significant disruptions in renal function, blood lipids, electrolytes, and tubulointerstitial architecture, alongside heightened OS, HIF pathway activation, and inflammatory responses in rats. In vivo, MZWT effectively ameliorated proteinuria, renal dysfunction, lipid and electrolyte imbalances, and renal tissue damage; it also suppressed OS, HIF pathway activation, epithelial-mesenchymal transition (EMT) in proximal tubular epithelial cells, and reduced the production of inflammatory cytokines and collagen fibers. In vitro findings demonstrated that MZWT decreased apoptosis, reduced ROS production, curbed OS, HIF pathway activation, and EMT in proximal tubular epithelial cells, and diminished the output of inflammatory cytokines and collagen.

Conclusion

OS and hypoxic responses significantly contribute to TIF development. MZWT mitigates these responses in renal proximal tubular epithelial cells, thereby delaying the progression of CRF.

A Molecular Perspective on HIF-1α and Angiogenic Stimulator Networks and Their Role in Solid Tumors: An Update

Hypoxia-inducible factor-1α (HIF-1α) is a major transcriptional factor, which plays an important role in cellular reprogramming processes under hypoxic conditions, which facilitate solid tumors' progression. HIF-1α is directly involved in the regulation of the angiogenesis, metabolic reprogramming, and extracellular matrix remodeling of the tumor microenvironment. Therefore, an in-depth study on the role of HIF-1α in solid tumor malignancies is required to develop novel anti-cancer therapeutics. HIF-1α also plays a critical role in regulating growth factors, such as the vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor, in a network manner. Additionally, it plays a significant role in tumor progression and chemotherapy resistance by regulating a variety of angiogenic factors, including angiopoietin 1 and angiopoietin 2, matrix metalloproteinase, and erythropoietin, along with energy pathways. Therefore, this review attempts to provide comprehensive insight into the role of HIF-1α in the energy and angiogenesis pathways of solid tumors.

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.

Hemin versus erythropoietin: Possible role in Nrf2/HO-1 signaling pathway in rats with nephrotoxicity

BACKGROUND AND AIM

Gentamycin-induced nephrotoxicity is related to stimulation of oxidative stress and inflammatory cascades leading to apoptotic renal damage. Heme oxygenase-1 (HO-1) induction considered to be an adaptive response against oxidative tissue damage. Our study aimed to investigate the possible nephroprotective role of HO-1 inducers (hemin and erythropoietin (EPO)) and elucidate their potential underlying molecular mechanisms by assessing their antioxidant, anti-apoptotic, and anti-inflammatory properties.

METHODS

Kidney function markers (urea and creatinine), lipid peroxidation and antioxidant markers (MDA and GPx), inflammation and apoptotic markers (IL-6 and Bcl-2), and the relative gene expression levels of Nrf2 and HO-1 were assessed. Histopathological changes of the kidney were examined.

RESULTS

Nephrotoxic rats pretreated with hemin showed significant decrease in serum level of urea, creatinine, and MDA, compared to non-treated group. The kidney tissues also showed significant elevation of Bcl2 level, but significant decrease of IL-6, compared to non-treated group. Moreover, hemin pre-treatment significantly upregulated gene expression of Nrf2 and HO-1 in kidney tissue to near the normal control group. On the other hand, pretreatment with EPO showed significant upregulation of HO-1 gene expression but didn't show significant difference in Nrf2 gene expression compared to control group. The histopathological examination of kidney supported the biochemical results.

CONCLUSION

The current results proved that hemin rather than EPO, showed reno-protective effects in rats, which was mediated by activation of Nrf2 signaling pathway. This could be also attributed to the observed anti-inflammatory, antioxidant, and anti-apoptotic properties of hemin. In this regard, EPO showed lower potency.

Increased angiogenesis parallels cardiac tissue remodelling in experimental acute Trypanosoma cruzi infection

BACKGROUND

Angiogenesis has been implicated in tissue injury in several noninfectious diseases, but its role in Chagas disease (CD) physiopathology is unclear.

OBJECTIVES

The present study aimed to investigate the effect of Trypanosoma cruzi infection on cardiac angiogenesis during the acute phase of experimental CD.

METHODS

The signalling pathway involved in blood vessel formation and cardiac remodelling was evaluated in Swiss Webster mice infected with the Y strain of T. cruzi. The levels of molecules involved in the regulation of angiogenesis, such as vascular endothelial growth factor-A (VEGF-A), Flk-1, phosphorylated extracellular-signal-regulated protein kinase (pERK), hypoxia-inducible factor-1α (HIF-1α), CD31, α-smooth muscle actin (α-SMA) and also the blood vessel growth were analysed during T. cruzi infection. Hearts were analysed using conventional histopathology, immunohistochemistry and western blotting.

FINDINGS

In this study, our data demonstrate that T. cruzi acute infection in mice induces exacerbated angiogenesis in the heart and parallels cardiac remodelling. In comparison with noninfected controls, the cardiac tissue of T. cruzi-infected mice presented higher levels of (i) HIF-1α, VEGF-A, Flk-1 and pERK; (ii) angiogenesis; (iii) α-SMA+ cells in the tissue; and (iv) collagen -1 deposition around blood vessels and infiltrating throughout the myocardium.

MAIN CONCLUSIONS

We observed cardiac angiogenesis during acute experimental T. cruzi infection parallels cardiac inflammation and remodelling.