OTA-induced Nephrotoxicity Research Articles

Central role of Sigma-1 receptor in ochratoxin A-induced ferroptosis.

Ochratoxin A (OTA), a secondary fungal metabolite known for its nephrotoxic effects, is prevalent in various feeds and food items. Our recent study suggests that OTA-induced nephrotoxicity is linked to the Sigma-1 receptor (Sig-1R)-mediated mitochondrial pathway apoptosis in human proximal tubule epithelial-originated kidney-2 (HK-2) cells. However, the contribution of Sig-1R to OTA-induced nephrotoxicity involving other forms of regulated cell death, such as ferroptosis, remains unexplored. In this investigation, cell viability, malondialdehyde (MDA) levels, glutathione (GSH) levels, and protein expressions in HK-2 cells treated with OTA and/or Ferrostatin-1/blarcamesine hydrochloride/BD1063 dihydrochloride were assessed. The results indicate that a 24h-treatment with 1μM OTA significantly induces ferroptosis by inhibiting Sig-1R, subsequently promoting nuclear receptor coactivator 4 (NCOA4), long-chain fatty acid-CoA ligase 4 (ACSL4), arachidonate 5-lipoxygenase (ALOX5), autophagy protein 5 (ATG5), and ATG7, inhibiting ferritin heavy chain (FTH1), solute carrier family 7 member 11 (SLC7A11/xCT), glutathione peroxidase 4 (GPX4), peroxiredoxin 6 (PRDX6), and ferroptosis suppressor protein 1 (FSP1), reducing GSH levels, and increasing MDA levels (P < 0.05). In conclusion, OTA induces ferroptosis by inhibiting Sig-1R, subsequently promoting ferritinophagy, inhibiting GPX4/FSP1 antioxidant systems, reducing GSH levels, and ultimately increasing lipid peroxidation levels in vitro.

Farnesoid X Receptor Plays a Key Role in Ochratoxin A-Induced Nephrotoxicity by Targeting Ferroptosis In Vivo and In Vitro.

The mycotoxin ochratoxin A (OTA) causes nephrotoxicity, hepatotoxicity, and immunotoxicity in animals and humans. The farnesoid X receptor (FXR) is a member of the NR family and is highly expressed in the kidney, which has an antilipid production function. Ferroptosis is an iron-dependent form of regulated cell death involved in several pathophysiological cell death and kidney injury. The present study aims to evaluate the role of FXR and ferroptosis in OTA-induced nephrotoxicity in mice and HK-2 cells. Results showed that OTA induced nephrotoxicity as demonstrated by inducing the histopathological lesions and neutrophil infiltration of the kidney, increasing serum BUN, CRE, and UA levels, increasing Ntn-1, Kim-1, and pro-inflammatory cytokine expression, and decreasing IL-10 expression and the cell viability of HK-2 cells. OTA treatment also induced FXR deficiency, ROS release, MDA level increase, GSH content decrease, and 4-HNE production in the kidney and HK-2 cells. OTA treatment induced ferroptosis as demonstrated by increasing labile iron pool and lipid peroxidation levels as well as Acsl4, TFR1, and HO-1 mRNA and protein levels, decreasing GPX4 and FTH mRNA and protein expressions, and inducing mitochondrial injury. The FXR activator (GW4064) rescued the accumulation of lipid peroxides, intracellular ROS, and Fe2+, inhibited ferroptosis, and alleviated OTA-induced nephrotoxicity. The ferroptosis inhibitor (Fer-1) prevented ferroptosis and attenuated nephrotoxicity. Collectively, this study elucidates that FXR played a critical role in OTA-induced nephrotoxicity via regulation of ferroptosis, which provides a novel strategy against OTA-induced nephrotoxicity.

Excessive ER-phagy contributes to ochratoxin A-induced apoptosis.

The nephrotoxic secondary fungal metabolite ochratoxin A (OTA) is ubiquitously existed in foodstuffs and feeds. Although our earlier research provided preliminary evidence that endoplasmic reticulum (ER) was crucial in OTA-induced nephrotoxicity, more research is necessary to understand the fine-tune mechanisms involving ER stress (ERS), ER-phagy, and apoptosis. In the present study, the cell viability and protein expressions of human proximal tubule epithelial (HK-2) cells in response to OTA and/or chloroquine/rapamycin/sodium phenylbutyrate/tunicamycin were determined via cell viability assay, apoptosis analysis, and Western blot analysis. The findings showed that a 24 h-treatment of 0.25-4μM OTA could significantly reduced the cell viability (P<0.05), which notably increased with the addition of chloroquine and sodium phenylbutyrate, while decreased with the addition of rapamycin and tunicamycin as compared to group OTA (P<0.05). A 24 h-treatment of 1-4μM OTA could markedly induce apoptosis via increasing the protein expressions of GRP78, p-eIF2α, Chop, LC3B-II, Bak, and Bax, and inhibiting the protein expressions of DDRGK1, UBA5, Lonp1, Tex264, FAM134B, p-mTOR, p62, and Bcl-2 in HK-2cells (P<0.05). In conclusion, OTA activated ERS, unfolded protein response, and subsequent excessive ER-phagy, thus inducing apoptosis, and the vicious cycle between excessive ER-phagy and ERS could further promote apoptosis in vitro.

Ochratoxin A (OTA) Affect OATPs and PEPTs and Cause RenalDisease

Ochratoxin A (OTA) is a mycotoxin related to the kidneys. There is a consensus that the primary route in which OTAis excreted into the urine is via tubular secretion, possibly through the organic anion transport system. There are somekinds of multipiece organic anion-transporting polypeptides (OATPs), ATP-binding cassettes (ABC) transporters, andtransporters such as organic anion transporters (OATs). These renal transporters are essential in exacerbating OTAinduced nephrotoxicity as OTA penetrates the cell membrane. This work concluded that the renal tubule’s reabsorptionand secretion of OTA might play an essential role in OTA accumulation and nephrotoxicity. Also, it tells us it is essentialto consider the impact of albumin binding on transport in vitro when considering the clearance of OTA in vivo.

Lonp1 and Sig-1R contribute to the counteraction of ursolic acid against ochratoxin A-induced mitochondrial apoptosis.

Ochratoxin A (OTA), a secondary fungal metabolite with nephrotoxicity, is widespread in numerous kinds of feeds and foodstuffs. Ursolic acid (UA), a water-insoluble pentacyclic triterpene acid, exists in a wide range of food materials and medicinal plants. Our earlier researches provided preliminary evidence that mitochondria- and mitochondria-associated endoplasmic reticulum membranes (MAMs)-located stress-responsive Lon protease 1 (Lonp1) had a protective function in OTA-induced nephrotoxicity, and the renoprotective function of UA against OTA partially due to Lonp1. However, whether other MAMs-located protiens, such as endoplasmic reticulum stress (ERS)-responsive Sigma 1-type opioid receptor (Sig-1R), contribute to the protection of UA against OTA-induced nephrotoxicity together with Lonp1 needs further investigation. In this study, the cell viability, reactive oxygen species, and protein expressions of human proximal tubule epithelial-originated kidney-2 (HK-2) cells varied with OTA and/or UA/CDDO-me/AVex-73/Sig-1R siRNA treatments were determined. Results indicated that a 24 h-treatment of 5μM OTA could significantly induce mitochondrial-mediated apoptosis via repressing Lonp1 and Sig-1R, thereby enhancing the protein expressions of GRP78, p-PERK, p-eIF2α, CHOP, IRE1α, and Bax, and inhibiting the protein expression of Bcl-2 in HK-2cells, which could be remarkably relieved by a 2 h-pre-treatment of 4μM UA (P<0.05). In conclusion, through mutual promotion between Lonp1 and Sig-1R, UA could effectively relieve OTA-induced apoptosis in vitro and break the vicious cycle between oxidative stress and ERS, which activated the mitochondrial apoptosis pathway.

Ochratoxin A induces endoplasmic reticulum stress and fibrosis in the kidney via the HIF-1α/miR-155-5p link.

Ochratoxin A (OTA) is a ubiquitous fungal toxin found in agricultural products and foods that is toxic to both humans and animals. OTA mainly affects kidney, but the mechanisms underlying OTA-induced nephrotoxicity remain not fully understood. MicroRNA (miRNA) is involved in key cellular processes. The toxic mechanism and regulatory effects of miRNAs on OTA toxicity in kidney, and particularly the role of HIFα-1/miR-155-5p on OTA-caused ER stress and fibrosis, were investigated in this study. OTA induced hypoxia-like conditions such as ER stress and fibrosis in HK-2 cells and renal tissues via modulating HIF-1α, which was followed by regulation of ER stress-related proteins (GRP78 and ATF-4), as well as fibrosis-related markers (fibronectin, α-SMA, and E-cadherin). Notably, a total of 62 miRNAs showed significant differential expression in kidney of OTA-treated mice. Under OTA exposure, HIF-1α enhanced miR-155-5p expression, causing ER stress and fibrosis in HK-2 cells. HIF-1α knockdown decreased OTA-induced miR-155-5p expression as well as ER stress and fibrotic responses, whereas miR-155-5p overexpression restored this. Our data suggest that OTA enhances ER stress and fibrosis in the kidney through upregulating the HIF-1α/miR-155-5p link.

Low doses of fumonisin B1 exacerbate ochratoxin A-induced renal injury in mice and the protective roles of heat shock protein 70

Fumonisin B1 (FB1) and ochratoxin A (OTA) possess nephrotoxicity to animals and widely co-exist in food and feedstuffs. FB1 rarely, while OTA often, causes toxicosis in animals. Heat shock protein 70 (Hsp70) resists lung injury induced by pneumolysin, but whether Hsp70 could remission mycotoxins-induced renal injury is still unknown. The present study aims to explore the impacts of nontoxic doses of FB1 on OTA-induced nephrotoxicity and the protective roles of Hsp70. In the mycotoxins-challenge experiment, ICR mice were co-exposed to nontoxic doses of FB1 (0, 0.2, 0.5, 1.0 mg/kg bw, IP) and toxic dose of OTA (0.4 mg/kg bw, IP) for 16 d. The results showed that the levels of BUN, Cr, MDA in serum, the Cyto C in renal tubes or glomerulus, pro-apoptosis genes and p-JNK protein expression in kidney were significantly increased. Histopathological results revealed the glomerular swelling. The above all indexes were dose-dependent. In the protection experiment, the mice were pretreated with the eukaryotic plasmid of pEGFP-C3-Hsp70, these increasing parameters in the mycotoxins-challenge experiment were reversed. In vitro, after pK-15 cells were treated with 8 μM FB1 and 5 μM OTA for 48 h, the mitochondrial membrane potential was significantly reduced, mitochondrial ROS was remarkably increased, more Cyto C was leaked from mitochondria into cytoplasm, and pro-apoptosis genes were significantly up-regulated. After the Hsp70 level was up-regulated by pEGFP-C3-Hsp70 or ML346 in pK-15 cells, these above indexes were reversed. However, activation of JNK by anisomycin significantly suppressed the protective effects of Hsp70. Our results demonstrate that the nontoxic doses of FB1 exacerbate the toxic dose of OTA-induced renal injury, while Hsp70 alleviates renal injury by inhibiting the JNK/MAPK signaling pathway. Hsp70 up-regulation may be an efficient strategy for protecting against tissue damage and bio-function impairment induced by co-exposure to FB1 and OTA.

Taurine alleviates ochratoxin A-induced pyroptosis in PK-15 cells by inhibiting oxidative stress.

Ochratoxin A (OTA) is one of the most harmful mycotoxins, which can cause multiple toxicological effects, especially nephrotoxicity in animals and humans. Taurine is an essential amino acid with various biological functions such as anti-inflammatory and anti-oxidation. However, the protective effect of taurine on OTA-induced nephrotoxicity and pyroptosis had not been reported. Our results showed that OTA exposure induced cytotoxicity and oxidative stress in PK-15 cells, including reactive oxygen species (ROS) accumulation, increased mRNA levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), and decreased mRNA levels of catalase (CAT), glutathione peroxidase 1 (GPx1), and glutathione peroxidase 4 (GPx4). In addition, OTA treatment induced pyroptosis by increasing the expressions of pyroptosis-related proteins NLRP3, GSDMD, Caspase-1 P20, ASC, Pro-caspase-1, and IL-1β. Meanwhile, taurine could alleviate OTA-induced pyroptosis and cytotoxicity, as well as reduce ROS level, COX-2, and iNOS mRNA levels, and increase the mRNA levels of the antioxidant enzyme in PK-15 cells. Taken together, taurine alleviated OTA-induced pyroptosis in PK-15 cells by inhibiting ROS generation and altering the activity of antioxidant enzymes, thereby attenuating its nephrotoxicity.

Antioxidant and antiapoptotic effects of quercetin against ochratoxin A-induced nephrotoxicity in broiler chickens

The mycotoxin ochratoxin A (OTA) is produced by the fungi Aspergillus and Penicillium. The flavonoid quercetin (QUE) is distinguished by its antioxidant, anti-inflammatory, and antiapoptotic properties. This study was designed to determine whether QUE can protect broiler chickens against OTA-induced nephrotoxicity. Forty broiler chicks were randomly divided into four equal groups: control, OTA, QUE, and OTA + QUE. For 6 weeks, OTA (0.5 mg/kg) and/or QUE (0.5 g/kg) were added to the diet of chickens. The results demonstrated that OTA exposure increased serum levels of creatinine, uric acid, and blood urea nitrogen. OTA exposure also increased renal malondialdehyde content but decreased renal antioxidants. OTA-exposed chickens exhibited multiple pathological kidney lesions. Moreover, OTA exposure induced apoptosis in renal tissue, which was manifested by the up-regulation of proapoptotic genes and down-regulation of antiapoptotic genes via the suppression of the PI3K/AKT pathway. In addition, coadministration of QUE and OTA mitigated most of these nephrotoxic effects.

Ochratoxin A treated rat derived urinary exosomes enhanced cell growth and extracellular matrix production in normal kidney cells through modulation of TGF-β1/smad2/3 signaling pathway

AimsKidney is the main target organ for ochratoxin A (OTA) toxicity; however, the mechanism(s) involved in OTA-induced nephrotoxicity is not fully understood. Recently, exosomes, nano-sized vesicles have been found to play an important role in promotion and progression of disease as well as environmental toxicant-induced patho-physiology of toxicity. Hence, we aimed to investigate the role of exosomes in OTA-mediated nephrotoxicity. Main methodsMale Wistar rats were divided in to two groups. Rats of one group were treated with OTA (210 μg/kg b. wt) and another with vehicle control through oral gavage (5 days/week) for 270 days. At the end of experiment, exosomes concentrations from rat's urine were measured. To examine the OTA-induced nephrotoxicity, histopathology was performed using H & E, Masson's trichome and PAS staining. For mechanistic study, normal rat kidney (NRK52E) cells were exposed with either vehicles treated rat's urinary exosomes (NEx) or OTA treated rat's urinary exosomes (OEx) and effects on cell proliferation, cell growth, extracellular matrix production and TGF-β1/smad2/3 pathway was analyzed. Key findingsOTA treatment to Wistar rats caused histopathological changes such as tubular degeneration, glomeruli shrinkage and hypercellularity in kidney tissue. Interestingly, OTA treated rat's urine has more exosomes secretion. Moreover, treatment of NRK52E cells with OEx caused increased cell proliferation, cell growth, enhanced the expression of extracellular matrix proteins and activation of TGF-β1/smad2/3 pathway. SignificanceOur investigations exogenous exposure of OTA derived urinary exosomes caused TGF-β1/smad2/3 pathway-mediated activation of pro-fibrotic changes in kidney will helpful for deeper understanding the OTA-induced nephrotoxicity.

Ochratoxin A induces NLRP3 inflammasome-mediated pyroptosis via activation of ROS modulated by autophagy in vitro

Ochratoxin A (OTA), one of the major food contaminating mycotoxins, has been reported to cause renal fibrosis through pyroptosis, but the detailed mechanism of its nephrotoxicity remains to be further investigated. Autophagy can be seen in the physiological and pathological processes of the body, and whether its role is positive or negative has not been fully elucidated. The aim of this paper was to explore the role of autophagic-inflammasomal pathway on pyroptosis caused by low levels of OTA in vitro. The results showed that OTA dose-dependently decreased cell viability in PK-15 cells and the half-maximal inhibitory concentration (IC50) was 5.9 µM. OTA could significantly increase pro-inflammatory cytokines (TNF-α, IL-1β, IL-18, IL-6) expression, induced pyroptosis and NLRP3 inflammasome formation at 1.0–4.0 µM for 48 h according to the results of qPCR, Western blotting, Immunofluorescence staining and morphologic observation. But MCC950 (an inhibitor of NLRP3) treatment or caspase-1 (sicaspase-1) knockdown could restore these changes. Additionally, we further found that reactive oxygen species (ROS) contributed to OTA-induced NLRP3 inflammasome and pyroptosis in PK-15 cells as indicated by Western blotting and immunofluorescence. Besides, we indicated that OTA induced autophagy via AKT/mTOR signaling pathway. And 3-MA (an inhibitor of autophagy) treatment or ATG5 (siATG5) knockdown enhanced ROS levels and NLRP3 inflammasome formation exposed to OTA. Taken together, our results elaborated that ROS/NLRP3-inlflammasome-mediated pyroptosis could be involved in the low levels of OTA-induced nephrotoxicity, which was negatively regulated by autophagy.

Combination of zinc and selenium alleviates ochratoxin A-induced fibrosis via blocking ROS-dependent autophagy in HK-2 cells

BackgroundOchratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium. The key target organ of OTA toxicity is the kidney, which has a significant impact on human health. Recently, nutrition regulation is suggested to be an effective protection against mycotoxins contamination. The current study investigated the combined protective effects of zinc and selenomethionine (SeMet) (a major component of organic selenium) on OTA-induced renal fibrosis and their potential mechanisms in human renal proximal tubule epithelial cells (HK-2 cells). MethodsCytotoxicity of different concentrations of OTA, zinc and SeMet on HK-2 cells was detected by cell viability, lactate dehydrogenase (LDH) and apoptotic nuclei assays. The expression of fibrosis biomarkers was detected by Real-Time PCR, western blotting and indirect immunofluorescence assays. The production of reactive oxygen species (ROS) was detected by ROS assay kit. The protein expression of autophagy biomarkers was detected by western blotting assay. ResultsCytotoxicity was induced by OTA treatment in a dose-dependent manner, and it was attenuated by zinc or SeMet application in HK-2 cells. Zinc or SeMet application also down-regulated the expression of fibrosis biomarkers, and the combination of them displayed better effects. In addition, OTA increased intracellular ROS level and activated autophagy in a dose-dependent manner, and it was reversed by zinc and SeMet combined application. With the treatment of hydrogen peroxide (H2O2) or rapamycin (the specific activator of autophagy), the combined protective effects of zinc and SeMet were abolished. ConclusionsZinc and SeMet application alleviated OTA-induced cytotoxicity and fibrosis in HK-2 cells. Combination of them was more effective than its individual application. The present study manifest novel insight about the alleviation of OTA-induced nephrotoxicity by nutrition regulation, and had a guiding effect on the clinical supplementation of nutritional elements.

AZADIRACHTA INDICA OIL AS PROTECTOR OF CHRONIC OCHRATOXIN-INDUCED NEPHROTOXICITY

Ochratoxin A (OTA) mycotoxin affects protein synthesis, metabolic oxidative pathways and ROS mediation. In the present study, we investigate the antioxidative-therapeutic potential of Azadirachta Indica Oil (A. indica) against chronic (28 days) OTA-induced nephrotoxicity. Balb/c male mice were exposed to i.e., (1) controls; (2) A. indica treated (120 mg/kg b. wt. i.p., given every two days); (3) c) OTA treated (Isolate D2306, 1.25 mg/kg b.wt., i.p., given every two days); d) A. indica (120 mg/kg b.wt., i.p.) administered 2h prior to OTA-administration. Till the end of the 28 experimental days of chronic OTA-nephrotoxicity, the mortality rate (±0) was not observed in mice. Kidney tissue was subjected for the determination of biochemical indexes (the MDA ratio, and antioxidant capability of SOD, and GSH) and EPR- ROS productions. OTA-exposure resulted in twofold significant increases in SOD (p&lt;0.004), GSH (p&lt;0.05) and malondialdehyde (MDA) levels (p&lt;0.00), compared to controls. Further, a nephro-cells experiment was performed to investigate the oxidative stress-protective action of A. indica. Our results showed that A. indica oil and A. indica +OTA combination inhibited OTA-induced nephrotoxicity via a significant reduction of lipid peroxidation (p&lt;0.003), ROS production (p&lt;0.005), and endogenous antioxidant activation. Thus, it can be concluded that A. indica treatment neutralized chronic OTA-induced nephrotoxicity, not only by reducing lipid peroxidation but also by improving antioxidant status. Through the present experiments, it was demonstrated that A. indica has protective potential in nephron-inflammations.

Selenomethionine alleviated Ochratoxin A induced pyroptosis and renal fibrotic factors expressions in MDCK cells.

Ochratoxin A (OTA) is universally known to induce nephrotoxicity via inducing oxidative stress and apoptosis, inhibiting protein synthesis and activating autophagy. Our previous studieshave proved that OTA induces nephrotoxicity in vitro and in vivo by adjusting the NOD-like receptor protein 3 (NLRP3) inflammasome activation and caspase-1-dependent pyroptosis. Based on these findings, we further investigated the protective role of selenomethionine (SeMet) on OTA-caused nephrotoxicity using the Madin-Darby canine kidney (MDCK) epithelial cells as anin vitro model, proposing to offer a new way for remedyingOTA-induced nephrotoxicity by nutritional manipulation. We measured the cell vitality, lactate dehydrogenase (LDH) activity and the expression of renal fibrotic genes, NLRP3 inflammasome and pyroptosis related genes. MTT and LDH results indicated that SeMet supplementation significantly mitigated 2.0 μg/ml OTA-induced cytotoxicity in MDCK cells (p < 0.05). Meanwhile, SeMet alleviated OTA induced increase of reactive oxygen species in MDCK cells. Then, the expressions of α-SMA, Vimentin, and TGF-β were detected both in mRNA and protein levels. The results indicated 8 μM SeMet supplementation could significantly downregulate the expression of OTA-induced renal fibrosis-related genes (p < 0.05). In addition, the upregulation of OTA-induced NLRP3 inflammasome and pyroptosis downstream genes was also significantly inhibited by 8 μM of SeMet (p < 0.05). In summary, SeMet could alleviate OTA-induced renal fibrotic genes expression and reduce NLRP3-caspase-1-dependent pyroptosis. Therefore, SeMet supplementation may become an effective approach for preserving animals from renal injury exposed to OTA.

Ochratoxin A-Induced Nephrotoxicity: Up-to-Date Evidence.

Ochratoxin A (OTA) is a mycotoxin widely found in various foods and feeds that have a deleterious effect on humans and animals. It has been shown that OTA causes multiorgan toxicity, and the kidney is the main target of OTA among them. This present article aims to review recent and latest intracellular molecular interactions and signaling pathways of OTA-induced nephrotoxicity. Pyroptosis, lipotoxicity, organic anionic membrane transporter, autophagy, the ubiquitin-proteasome system, and histone acetyltransferase have been involved in the renal toxicity caused by OTA. Meanwhile, the literature reviewed the alternative or method against OTA toxicity by reducing ROS production, oxidative stress, activating the Nrf2 pathway, through using nanoparticles, a natural flavonoid, and metal supplement. The present review discloses the molecular mechanism of OTA-induced nephrotoxicity, providing opinions and strategies against OTA toxicity.

Selective Activation of Endoplasmic Reticulum Stress by Reactive-Oxygen-Species-Mediated Ochratoxin A-Induced Apoptosis in Tubular Epithelial Cells.

Ochratoxin A (OTA), one of the major food-borne mycotoxins, impacts the health of humans and livestock by contaminating food and feed. However, the underlying mechanism of OTA nephrotoxicity remains unknown. This study demonstrated that OTA induced apoptosis through selective endoplasmic reticulum (ER) stress activation in human renal proximal tubular cells (HK-2). OTA increased ER-stress-related JNK and precursor caspase-4 cleavage apoptotic pathways. Further study revealed that OTA increased reactive oxygen species (ROS) levels, and N-acetyl cysteine (NAC) could reduce OTA-induced JNK-related apoptosis and ROS levels in HK-2 cells. Our results demonstrate that OTA induced ER stress-related apoptosis through an ROS-mediated pathway. This study provides new evidence to clarify the mechanism of OTA-induced nephrotoxicity.

Curcumin Modulates Nitrosative Stress, Inflammation, and DNA Damage and Protects against Ochratoxin A-Induced Hepatotoxicity and Nephrotoxicity in Rats.

Ochratoxin A (OTA) is a fungal toxin of critical concern for food safety both for human health and several animal species, also representing a cancer threat to humans. Curcumin (CURC) is a natural polyphenol that has anti-apoptotic, anti-inflammatory, and antioxidant effects. The aim of this study was to investigate the cytoprotective effect of CURC against OTA-induced nephrotoxicity and hepatotoxicity through the study of the nitrosative stress, pro-inflammatory cytokines, and deoxyribonucleic acid (DNA) damage. Sprague Dawley rats were daily treated with CURC (100 mg/kg b.w.), OTA (0.5 mg/kg b.w), or CURC with OTA by oral gavage for 14 days. Our results demonstrated that OTA exposure was associated with significant increase of pro-inflammatory and DNA oxidative-damage biomarkers. Moreover, OTA induced the inducible nitric oxide synthase, (iNOS) resulting in increased nitric oxide (NO) levels both in kidney and liver. The co-treatment OTA + CURC counteracted the harmful effects of chronic OTA treatment by regulating inflammation, reducing NO levels and oxidative DNA damage in kidney and liver tissues. Histology revealed that OTA + CURC treatment determinates mainly an Iba1+ macrophagic infiltration with fewer CD3+ T-lymphocytes in the tissues. In conclusion, we evidenced that CURC exerted cytoprotective and antioxidant activities against OTA-induced toxicity in rats.

Non-cytotoxic dosage of fumonisin B1 aggravates ochratoxin A-induced nephrocytotoxicity and apoptosis via ROS-dependent JNK/MAPK signaling pathway

Ochratoxin A (OTA) and fumonisin B1 (FB1), two of the most toxicologically important mycotoxins, often coexist in a variety of foodstuff and feed in humans and animals. Because of the low content of FB1 in foodstuff and feed, alone harmfulness of FB1 is often ignored. However, it is unknown whether the lower dosage of FB1 aggravates the toxicity of other mycotoxins. In this article, we aimed to investigate the effects of the lower dosage of FB1 on OTA-induced nephrotoxicity and apoptosis, and its underlying mechanism in porcine kidney cells (PK-15). Our current study showed that the non-cytotoxic concentration of FB1 (8 μM) could enhance OTA(5 μM)-induced nephrocytotoxicity and the expression of pro-apoptosis-associated genes in PK-15 cells. We also observed that the production of reactive oxygen species (ROS) was increased. However, the expression of pro-apoptosis-associated genes were down-regulated when the N-acetylcysteine (NAC), a ROS scavenger, was used in our experiment. Besides, we found that the combined toxins could increase the protein expression of p-JNK instead of p-p38 and p-ERK. Pretreatment with SP600125, a JNK inhibitor, could significantly block the promotion effects of FB1 on OTA-induced nephrocytotoxicity and apoptosis. The protein expression of p-JNK was also inhibited and the promotion effects of FB1 were significantly alleviated when NAC was used. In conclusion, the non-cytotoxic dosage of FB1 could aggravate the nephrocytotoxicity and apoptosis caused by OTA via ROS-dependent JNK/MAPK signaling pathway.

Central role of TRAP1 in the ameliorative effect of oleanolic acid on the mitochondrial-mediated and endoplasmic reticulum stress-excitated apoptosis induced by ochratoxin A

Ochratoxin A (OTA) is a nephrotoxic mycotoxin that is widely distributed in foodstuffs and feeds, meanwhile oleanolic acid (OA) is ubiquitous in various fruit skins, food materials, and medicinal herbs. Due to that OA has a nephroprotective effect, it has the poteintial to counteract OTA-induced nephrotoxicity by nutritional intervention of OA. Furthermore, tumor necrosis factor receptor-associated protein 1 (TRAP1) acts as the core of endoplasmic reticulum (ER)-mitochondria crosstalk, becoming our focus in the mechanism investigation. In this study, the cell viability, apoptosis rate, and protein expressions of human proximal tubule epithelial-originated kidney-2 (HK-2) cells in response to OTA and/or OA were determined. Results indicated that a 24 h-treatment of 1-5 μM OTA could notably induce mitochondrial-mediated and ER stress (ERS)-excitated apoptosis via inhibiting TRAP1, thereby activating CypD, Bax, Cyt-C, Cleaved Caspase-9, Cleaved Caspase-3, GRP78, p-PERK, p-eIF2α, ATF4, and CHOP and inhibiting Bcl-2 (P < 0.05). Results of the RNA interference of TRAP1 further ascertained its anti-apoptotic function via inhibiting CypD, Bax, GRP78, and CHOP and enhancing Bcl-2 (P < 0.05). The pre-treatment of 2 μM OA for 2 h could remarkably relieve OTA-induced suppression of TRAP1 (P < 0.05). In conclusion, TRAP1 played a central role in the ameliorative effect of OA on the mitochondrial-mediated and ERS-excitated apoptosis induced by OTA.

Regulation of taurine in OTA-induced apoptosis and autophagy

Ochratoxin A (OTA), one of the most deleterious mycotoxins, could cause a variety of toxicological effects especially nephrotoxicity in animals and humans. Taurine, a wide-distributed cytoprotective amino acid, plays an important role as a basic factor for maintaining cellular integrity homeostasis. However, the potential effect of taurine in OTA-induced nephrotoxicity remains unknown. In the present study, we demonstrated that OTA treatment at 4.0–8.0 μM increased apoptosis in PK-15 cells as shown by increased the ratio of apoptosis and protein expression of Bax and cleaved-caspase-3, decreased protein expression of Bcl-2. Meantime, OTA treatment triggered autophagy, as indicated by markedly increased the protein expression of LC3-II and fluorescence intensity of GFP-LC3 dots. Taurine supplementation decreased OTA-induced cytotoxicity and attenuated apoptosis as shown by the decreased Annexin V/PI staining and the decreased expression of apoptosis-related proteins including Bax and caspase-3. Meanwhile, taurine attenuated OTA-induced autophagy by decreased the protein expression of LC3-II and fluorescence intensity of GFP-LC3 dots to maintain cellular homeostasis. In conclusion, taurine treatment could alleviate OTA-induced apoptosis and inhibit the triggered autophagy in PK-15 cells. Our study provides supportive data for the potential roles of taurine in reducing OTA-induced renal toxicity.