Identifying novel aryl hydrocarbon receptor (AhR) modulators from clinically approved drugs: In silico screening and In vitro validation.

The aryl hydrocarbon receptor (AhR) functions as a vital ligand-activated transcription factor, governing both physiological and pathophysiological processes. Notably, it responds to xenobiotics, leading to a diverse array of outcomes. In the context of drug repurposing, we present here a combined approach of utilizing structure-based virtual screening and molecular dynamics simulations. This approach aims to identify potential AhR modulators from Drugbank repository of clinically approved drugs. By focusing on the AhR PAS-B binding pocket, our screening protocol included binding affinities calculations, complex stability, and interactions within the binding site as a filtering method. Comprehensive evaluations of all DrugBank small molecule database revealed ten promising hits. This included flibanserin, butoconazole, luliconazole, naftifine, triclabendazole, rosiglitazone, empagliflozin, benperidol, nebivolol, and zucapsaicin. Each exhibiting diverse binding behaviors and remarkably very low binding free energy. Experimental studies further illuminated their modulation of AhR signaling, and showing that they are consistently reducing AhR activity, except for luliconazole, which intriguingly enhances the AhR activity. This work demonstrates the possibility of using computational modelling as a quick screening tool to predict new AhR modulators from extensive drug libraries. Importantly, these findings hold immense therapeutic potential for addressing AhR-associated disorders. Consequently, it offers compelling prospects for innovative interventions through drug repurposing.

Dimethylmonothioarsinic acid (DMMTAV) differentially modulates the expression of AHR-regulated cytochrome P450 1A enzymes in vivo and in vitro.

Dimethylmonothioarsinic acid (DMMTAV), a pentavalent thio-arsenic derivative, has been found in bodily fluids and tissues including urine, liver, kidney homogenates, plasma, and red blood cells. Although DMMTAV is a minor metabolite in humans and animals, its substantial toxicity raises concerns about potential carcinogenic effects. This toxicity could be attributed to arsenicals' ability to regulate cytochrome P450 1 A (CYP1A) enzymes, pivotal in procarcinogen activation or detoxification. The current study investigates DMMTAV's impact on CYP1A1/2 expression, individually and in conjunction with its inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). C57BL/6 mice were intraperitoneally injected with 6 mg/kg DMMTAV, alone or with 15 µg/kg TCDD, for 6 and 24 h. Similarly, Hepa-1c1c7 cells were exposed to DMMTAV (0.5, 1, and 2 µM) with or without 1 nM TCDD for 6 and 24 h. DMMTAV hindered TCDD-induced elevation of Cyp1a1 mRNA, both in vivo (at 6 h) and in vitro, associated with reduced CYP1A regulatory element activation. Interestingly, in C57BL/6 mice, DMMTAV boosted TCDD-induced CYP1A1/2 protein and activity, unlike Hepa-1c1c7 cells where it suppressed both. DMMTAV co-exposure increased TCDD-induced Cyp1a2 mRNA. While Cyp1a1 mRNA stability remained unchanged, DMMTAV negatively affected protein stability, indicated by shortened half-life. Baseline levels of CYP1A1/2 mRNA, protein, and catalytic activities showed no significant alterations in DMMTAV-treated C57BL/6 mice and Hepa-1c1c7 cells. Taken together, these findings indicate, for the first time, that DMMTAV differentially modulates the TCDD-mediated induction of AHR-regulated enzymes in both liver of C57BL/6 mice and murine Hepa-1c1c7 cells suggesting that thio-arsenic pentavalent metabolites are extremely reactive and could play a role in the toxicity of arsenic.

Differential Modulatory Effects of Methylmercury (MeHg) on Ahr-regulated Genes in Extrahepatic Tissues of C57BL/6 Mice.

Methylmercury (MeHg) and 2,3,7,8-tetrachlorodibenzodioxin (TCDD) are potent environmental pollutants implicated in the modulation of xenobiotic-metabolizing enzymes, particularly the cytochrome P450 1 family (CYP1) which is regulated by the aryl hydrocarbon receptor (AHR). However, the co-exposure to MeHg and TCDD raises concerns about their potential combined effects, necessitating thorough investigation. The primary objective of this study was to investigate the individual and combined effects of MeHg and TCDD on AHR-regulated CYP1 enzymes in mouse extrahepatic tissues. Therefore, C57BL/6 mice were administrated with MeHg (2.5 mg/kg) in the absence and presence of TCDD (15 µg/kg) for 6 and 24 h. The AHR-regulated CYP1 mRNA and protein expression levels were measured in the heart, lung, and kidney, using RT real-time PCR and western blot, respectively. Interestingly, treatment with MeHg exhibited mainly inhibitory effect, particularly, it decreased the basal level of Cyp1a1 and Cyp1a2 mRNA and protein, and that was more evident at the 24 h time point in kidney followed by heart. Similarly, when mice were co-exposed, MeHg was able to reduce the TCDD-induced Cyp1a1 and Cyp1a2 expression, however, MeHg potentiated kidney Cyp1b1 mRNA expression, opposing the observed change on its protein level. Also, MeHg induced antioxidant NAD(P)H:quinone oxidoreductase (NQO1) mRNA and protein in kidney, while heme-oxygenase (HO-1) mRNA was up-regulated in heart and kidney. In conclusion, this study reveals intricate interplay between MeHg and TCDD on AHR-regulated CYP1 enzymes, with interesting inhibitory effects observed that might be significant for procarcinogen metabolism. Varied responses across tissues highlight the potential implications for environmental health.

The Effects of 16-HETE Enantiomers on Hypertrophic Markers in Human Fetal Ventricular Cardiomyocytes, RL-14 Cells.

BACKGROUND: Cytochrome P450 (CYP) metabolizes arachidonic acid to produce bioactive metabolites such as EETs and HETEs: mid-chain, subterminal, and terminal HETEs. Recent studies have revealed the role of CYP1B1 and its associated cardiotoxic mid-chain HETE metabolites in developing cardiac hypertrophy and heart failure. Subterminal HETEs have also been involved in various physiological and pathophysiological processes; however, their role in cardiac hypertrophy has not been fully defined. OBJECTIVE: The objective of the current study is to determine the possible effect of subterminal HETEs, R and S enantiomers of 16-HETE, on CYP1B1 expression in vitro using human cardiomyocytes RL-14 cells. METHODS: In the study, RL14 cell line was treated with vehicle and either of the 16-HETE enantiomers for 24 h. Subsequently, the following markers were assessed: cell viability, cellular size, hypertrophic markers, CYP1B1 gene expression (at mRNA, protein, and activity levels), luciferase activity, and CYP1B1 mRNA and protein half-lives. RESULTS: The results of the study showed that 16-HETE enantiomers significantly increased hypertrophic markers and upregulated CYP1B1 mRNA and protein expressions in RL-14 cell line. The upregulation of CYP1B1 by 16-HETE enantiomers occurs via a transcriptional mechanism as evidenced by transcriptional induction and luciferase reporter assay. Furthermore, neither post-transcriptional nor post-translational modification was involved in such modulation since there was no change in CYP1B1 mRNA and protein stabilities upon treatment with 16-HETE enantiomers. CONCLUSION: The current study provides the first evidence that 16R-HETE and 16S-HETE increase CYP1B1 gene expression through a transcriptional mechanism.

Methylmercury (MeHg) transcriptionally regulates NAD(P)H:quinone oxidoreductase 1 (NQO1) in Hepa-1c1c7 cells.

The detoxification of quinones through NAD(P)H:quinone oxidoreductase (NQO1) is a crucial mechanism to maintain cellular homeostasis. The exposure to heavy metals, specifically methylmercury (MeHg), induces several antioxidant enzymes, including NQO1. The nuclear factor erythroid 2-related factor-2 (NRF2) is known to regulate the expression of Nqo1 gene and also the aryl hydrocarbon receptor (AHR) is another Nqo1 gene regulator. This co-regulation prompted us to investigate which transcription factor (NRF2 or AHR) orchestrates the regulation of NQO1 expression upon MeHg exposure. Therefore, we investigated how MeHg can modulate the level of NQO1 expression by exposing Hepa-1c1c7 cells to several concentrations of MeHg with and without the addition of NQO1 inducers, DL-sulforaphane (SUL) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We found that the mRNA expression of Nqo1 is up-regulated by MeHg in time- as well as dose-dependent fashions. Additionally, MeHg increased the NQO1 at all expression levels with and without the presence of its inducers, SUL or TCDD. Furthermore, the MeHg-mediated increase of NQO1 expression was in parallel with a concurrent increase in the nuclear localization of NRF2 protein, but not that of AHR. Mechanistically, the antioxidant response element-driven reporter gene activity was induced by 215% upon MeHg exposure. Also, transfecting Hepa-1c1c7 with Nrf2 siRNA reduced the MeHg-induced NQO1 protein expression by 60%. In conclusion, our findings provide evidence supporting the hypothesis that MeHg upregulates the Nqo1 gene through a transcriptional mechanism at least in part via a NRF2-dependent mechanism.

Differential modulation of cytochrome P450 enzymes by arsenicals in non-human experimental models.

Arsenic is a hazardous heavy metalloid that imposes threats to human health globally. It is widely spread throughout the environment in various forms. Arsenic-based compounds are either inorganic compounds (iAs) or organoarsenicals (oAs), where the latter are biotically generated from the former. Exposure to arsenic-based compounds results in varying biochemical derangements in living systems, leading eventually to toxic consequences. One important target for arsenic in biosystems is the network of metabolic enzymes, especially the superfamily of cytochrome P450 enzymes (CYPs) because of their prominent role in both endobiotic and xenobiotic metabolism. Therefore, the alteration of the CYPs by different arsenicals has been actively studied in the last few decades. We have previously summarized the findings of former studies investigating arsenic associated modulation of different CYPs in human experimental models. In this review, we focus on non-human models to get a complete picture about possible CYPs alterations in response to arsenic exposure.

Arsenic trioxide (ATO) up-regulates cytochrome P450 1A (CYP1A) enzymes in murine hepatoma Hepa-1c1c7 cell line.

Arsenic trioxide (ATO) is a highly toxic arsenical which has been successfully exploited for treating acute promyelocytic leukemia (APL). Unfortunately, its therapeutic efficacy is accompanied by serious toxicities with undeciphered mechanisms. Cytochrome P450 1A (CYP1A) enzymes undergo modulation by arsenicals, with ensuing critical consequences regarding drug clearance or procarcinogen activation. Here, we investigated the potential of ATO to alter basal and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1/1A2 expressions. Mouse-derived hepatoma Hepa-1c1c7 cells were exposed to 0.63, 1.25, and 2.5 µM ATO with or without 1 nM TCDD. ATO increased TCDD-induced CYP1A1/1A2 mRNA, protein, and activity. Constitutively, ATO induced Cyp1a1/1a2 transcripts and CYP1A2 protein. ATO increased AHR nuclear accumulation and subsequently increased XRE-luciferase reporter activity. ATO enhanced CYP1A1 mRNA and protein stabilities. In conclusion, ATO up-regulates CYP1A in Hepa-1c1c7 cells transcriptionally, post-transcriptionally, and post-translationally. Therefore, ATO can be implicated in clearance-related interactions with CYP1A1/1A2 substrates, or in excessive activation of environmental procarcinogens.

Sex- and enantiospecific differences in the formation rate of hydroxyeicosatetraenoic acids in rat organs.

Hydroxyeicosatetraenoic acids (HETEs) are hydroxylated arachidonic acid (AA) metabolites that are classified into midchain, subterminal, and terminal HETEs. Hydroxylation results in the formation of R and S enantiomers for each HETE, except for 20-HETE. HETEs have multiple physiological and pathological effects. Several studies have demonstrated sex-specific differences in AA metabolism in different organs. In this study, microsomes from the heart, liver, kidney, lung, intestine, and brain of adult male and female Sprague-Dawley rats were isolated and incubated with AA. Thereafter, the enantiomers of all HETEs were analyzed by liquid chromatography-tandem mass spectrometry. We found significant sex- and enantiospecific differences in the formation levels of different HETEs in all organs. The majority of HETEs, especially midchain HETEs and 20-HETE, showed significantly higher formation rates in male organs. In the liver, the R enantiomer of several HETEs showed a higher formation rate than the corresponding S enantiomer (e.g., 8-, 9-, and 16-HETE). On the other hand, the brain and small intestine demonstrated a higher abundance of the S enantiomer. 19(S)-HETE was more abundant than 19(R)-HETE in all organs except the kidney. Elucidating sex-specific differences in HETE levels provides interesting insights into their physiological and pathophysiological roles and their possible implications for different diseases.

Modulation of cytochrome P450 1A (CYP1A) enzymes by monomethylmonothioarsonic acid (MMMTAV) in vivo and in vitro.

Inorganic arsenic (iAs) is a natural toxicant which, upon entering the biosphere, undergoes extensive biotransformation and becomes a portal for generating various organic intermediates/products. The chemical diversity of iAs-derived organoarsenicals (oAs) is accompanied by varying degree of toxicity that can be held responsible, at least partly, for the overall health outcome of the originally encountered parent inorganic molecule. Such toxicity may originate from arsenicals ability to modulate cytochrome P450 1A (CYP1A) enzymes, whose activity is critical in activating/detoxifying procarcinogens. In this study, we evaluated the effect of monomethylmonothioarsonic acid (MMMTAV) on CYP1A1 and CYP1A2 in absence and presence of their inducer; 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Therefore, C57BL/6 mice were intraperitoneally injected with 12.5 mg/kg MMMTAV, with or without 15 µg/kg TCDD for 6 and 24 h. Moreover, murine Hepa-1c1c7 and human HepG2 cells were treated with MMMTAV (1, 5, and 10 µM), with or without 1 nM TCDD for 6 and 24 h. MMMTAV significantly inhibited TCDD-mediated induction of CYP1A1 mRNA, both in vivo and in vitro. This effect was attributed to decreased transcriptional activation of CYP1A regulatory element. Interestingly, MMMTAV significantly increased TCDD-induced CYP1A1 protein and activity in C57BL/6 mice and Hepa-1c1c7 cells, while both were significantly inhibited by MMMTAV treatment in HepG2 cells. CYP1A2 mRNA, protein and activity induced by TCDD were significantly increased by MMMTAV co-exposure. MMMTAV had no effect on CYP1A1 mRNA stability or protein stability and did not alter their half-lives. At basal level, only CYP1A1 mRNA was significantly decreased in MMMTAV-treated Hepa-1c1c7 cells. Our findings show that MMMTAV exposure potentiates procarcinogen-induced catalytic activity of both CYP1A1 and CYP1A2 in vivo. This effect entails excessive activation of such procarcinogens upon co-exposure, with potentially negative health-related outcomes.

The Duality of Arsenic Metabolism: Impact on Human Health.

Arsenic is a naturally occurring hazardous element that is environmentally ubiquitous in various chemical forms. Upon exposure, the human body initiates an elimination pathway of progressive methylation into relatively less bioreactive and more easily excretable pentavalent methylated forms. Given its association with decreasing the internal burden of arsenic with ensuing attenuation of its related toxicities, biomethylation has been applauded for decades as a pure route of arsenic detoxification. However, the emergence of detectable trivalent species with profound toxicity has opened a long-standing debate regarding whether arsenic methylation is a detoxifying or bioactivating mechanism. In this review, we approach the topic of arsenic metabolism from both perspectives to create a complete picture of its potential role in the mitigation or aggravation of various arsenic-related pathologies.

Mercury and methylmercury differentially modulate hepatic cytochrome P450 1A1 and 1A2 in vivo and in vitro.

The cytochrome P450 1 A (CYP1A) subfamily enzymes are involved in the metabolic activation of several xenobiotics to toxic metabolites and reactive intermediates, resulting ultimately in carcinogenesis. Mercury and halogenated aromatic hydrocarbons (HAHs), typified by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are persistent environmental pollutants involved in the modulation of aryl hydrocarbon receptor (AHR) gene battery, including cytochrome P450 (CYP) genes. We previously investigated the effect of coexposure to either inorganic or organic mercury (Hg+2 and MeHg) with TCDD on CYP1A1 in vitro. Thus, we examined the impact of coexposure to Hg+2 or MeHg and TCDD on AHR-regulated genes (Cyp1a1/1a2) in vivo and in vitro. Therefore, male C57BL/6 mice were injected intraperitoneally with MeHg or Hg+2 (2.5 mg/kg) in the absence and presence of TCDD (15 µg/kg) for 6 or 24 h. The concentration-dependent effect of MeHg was examined in murine hepatoma Hepa1c1c7 cells. In vivo, both MeHg and Hg2+ inhibited the TCDD-mediated induction of Cyp1a1/1a2 mRNA levels. However, Only Hg2+ was able to inhibit the TCDD-mediated induction at posttranscriptional levels of CYP1A1/1A2 protein and catalytic activity, suggesting differential modulation effects by Hg+2 and MeHg. In addition, the inhibitory role of HO-1 (Heme oxygenase-1) on CYP1A activity induced by TCDD was investigated using a HO-1 competitive inhibitor, tin-mesoporphyrin, that partially restored the MeHg-mediated decrease in CYP1A1 activity. This study demonstrates that MeHg, alongside Hg2+ , can differentially modulate the TCDD-induced AHR-regulated genes (Cyp1a1/1a2) at different expression levels in C57BL/6 mice liver and Hepa1c1c7 cells.

Down-regulation of hepatic cytochromes P450 1A1 and 1A2 by arsenic trioxide (ATO) in vivo and in vitro: A role of heme oxygenase 1.

Arsenic trioxide (ATO) has evolved from an environmental threat to a successful therapy for acute promyelocytic leukemia (APL) and probably for solid tumors in the future. However, its efficacy comes at a cost of multi-organ toxicity whose mechanism remains unresolved. Arsenicals have been reported to modulate cytochrome P450 1A (CYP1A) enzymes, thus modifying activation/detoxification of drugs/procarcinogens. Therefore, this study aimed to investigate the possible effects of ATO on CYP1A1 and CYP1A2, in absence and presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) using in vivo and in vitro models. For this purpose, C57BL/6 mice were intraperitoneally injected with 8 mg/kg ATO with or without 15 µg/kg TCDD for 6 and 24 h. Furthermore, HepG2 cells were treated with ATO (1, 5, and 10 µM) with or without 1 nM TCDD for 6 and 24 h. ATO significantly inhibited TCDD-mediated induction of CYP1A1/1A2 mRNA, protein, and activity in both models. ATO differentially modulated CYP1A1/1A2 basal levels in vivo. We also demonstrated that ATO downregulates CYP1A through inhibiting the transcriptional activation of its regulatory element at both basal and inducible levels. Additionally, ATO significantly induced mRNA and protein of heme oxygenase 1 (HMOX1) in vivo and in vitro. In HepG2 cells, inhibition of HMOX1 by tin (IV) mesoporphyrin (IX) (SnMP) resulted in a partial restoration of the TCDD-mediated induction of CYP1A1 activity that was inhibited by ATO co-exposure. Our findings show that ATO alters both constitutive and inducible CYP1A1/1A2 expressions through transcriptional and HMOX1-mediated post-translational mechanisms. This implies the possible involvement of ATO in clearance-related consequences for the substrates of these enzymes such as drug-drug interactions or suboptimal toxicant elimination.

Arsenic: Various species with different effects on cytochrome P450 regulation in humans.

Arsenic is well-recognized as one of the most hazardous elements which is characterized by its omnipresence throughout the environment in various chemical forms. From the simple inorganic arsenite (iAsIII) and arsenate (iAsV) molecules, a multitude of more complex organic species are biologically produced through a process of metabolic transformation with biomethylation being the core of this process. Because of their differential toxicity, speciation of arsenic-based compounds is necessary for assessing health risks posed by exposure to individual species or co-exposure to several species. In this regard, exposure assessment is another pivotal factor that includes identification of the potential sources as well as routes of exposure. Identification of arsenic impact on different physiological organ systems, through understanding its behavior in the human body that leads to homeostatic derangements, is the key for developing strategies to mitigate its toxicity. Metabolic machinery is one of the sophisticated body systems targeted by arsenic. The prominent role of cytochrome P450 enzymes (CYPs) in the metabolism of both endobiotics and xenobiotics necessitates paying a great deal of attention to the possible effects of arsenic compounds on this superfamily of enzymes. Here we highlight the toxicologically relevant arsenic species with a detailed description of the different environmental sources as well as the possible routes of human exposure to these species. We also summarize the reported findings of experimental investigations evaluating the influence of various arsenicals on different members of CYP superfamily using human-based models.

Targeting arachidonic acid-related metabolites in COVID-19 patients: potential use of drug-loaded nanoparticles.

In March 2020, The World Health Organization (WHO) has declared that the coronavirus disease 2019 (COVID-19) is characterized as a global pandemic. As of September 2020, infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread to 213 countries and territories around the world, affected more than 31.5 million people, and caused more than 970,000 deaths worldwide. Although COVID-19 is a respiratory illness that mainly targets the lungs, it is currently well established that it is a multifactorial disease that affects other extra-pulmonary systems and strongly associated with a detrimental inflammatory response. Evidence has shown that SARS-CoV-2 causes perturbation in the arachidonic acid (AA) metabolic pathways; this disruption could lead to an imbalance between the pro-inflammatory metabolites of AA including mid-chain HETEs and terminal HETE (20-HETE) and the anti-inflammatory metabolites such as EETs and subterminal HETEs. Therefore, we propose novel therapeutic strategies to modulate the level of endogenous anti-inflammatory metabolites of AA and induce the patient's endogenous resolution mechanisms that will ameliorate the virus-associated systemic inflammation and enhance the primary outcomes in COVID-19 patients. Also, we propose that using nanoencapsulation of AA and its associated metabolites will contribute to the development of safer and more efficacious treatments for the management of COVID-19.

Cytochrome P450-mediated drug interactions in COVID-19 patients: Current findings and possible mechanisms.

At the end of 2019, the entire world has witnessed the birth of a new member of coronavirus family in Wuhan, China. Ever since, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has swiftly invaded every corner on the planet. By the end of April 2020, almost 3.5 million cases have been reported worldwide, with a death toll of about 250,000 deaths. It is currently well-recognized that patient's immune response plays a pivotal role in the pathogenesis of Coronavirus Disease 2019 (COVID-19). This inflammatory element was evidenced by its elevated mediators that, in severe cases, reach their peak in a cytokine storm. Together with the reported markers of liver injury, such hyperinflammatory state may trigger significant derangements in hepatic cytochrome P450 metabolic machinery, and subsequent modulation of drug clearance that may result in unexpected therapeutic/toxic response. We hypothesize that COVID-19 patients are potentially vulnerable to a significant disease-drug interaction, and therefore, suitable dosing guidelines with therapeutic drug monitoring should be implemented to assure optimal clinical outcomes.

Cytochrome P450-derived eicosanoids and inflammation in liver diseases.

Hepatic inflammation is a key pathologic mediator in a wide array of acute and chronic liver diseases. Hepatitis is a crucial driver of liver tissue damage provoking the progression to severe fibrosis, cirrhosis and hepatocellular carcinoma, irrespective of the etiologic cause. Inflammatory liver diseases are collectively considered one of the most critical public health risks. Cytochrome P450 (CYP) enzymes are superfamily of monooxygenases which possess the greater diversity of substrate structures amidst all other enzyme families. Members of omega-3 as well as omega-6 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid and arachidonic acid, respectively, can be metabolized by CYP isoforms leading to the production of biologically active lipid mediators called eicosanoids. CYP-derived eicosanoids have been shown to play significant roles in the pathophysiology and protection of multiple inflammatory liver diseases. In this review, we elucidate the intricate role of CYP-derived eicosanoids in inflammation in liver diseases paving the way for better therapeutic approaches.

Evaluation of the protective effect of Cystone against cisplatin-induced nephrotoxicity in cancer patients, and its influence on cisplatin antitumor activity.

PURPOSE: Evaluating the role of cystone, a polyherbal preparation, in protecting cancer patients against cisplatin-induced nephrotoxicity, and its impact on the cytotoxic activity of cisplatin. METHODS: A prospective open-label randomized controlled trial conducted on 49 cancer patients who received six cycles of 70 mg/m(2) cisplatin-based regimens. The study comprised two groups, a control group (A) in which 28 patients received cisplatin without cystone supplement, and an experimental group (B) in which 21 patients received cisplatin with cystone supplement. Renal function parameters including serum creatinine, creatinine clearance, blood urea, and serum cystatin C were compared between both groups throughout chemotherapy cycles. Patient response to treatment was evaluated in both groups after 3rd and 6th cycles. RESULTS: At the end of the study, mean levels of serum creatinine, blood urea, and serum cystatin C were significantly lower, whereas creatinine clearance was significantly higher in group (B) compared with group (A). In group (B), there was no significant difference between mean levels of renal markers at baseline and after completion of treatment; while significant changes were observed in group (A). Grading of acute kidney injury according to Common Terminology Criteria for Adverse Events revealed significantly better renal status among patients in group (B) "grades 0 and 1 in 76 and 24 % of the patients, respectively" compared with group (A) "grades 0, 1, and 2 in 36, 32, and 32 % of the patients, respectively". Based on Response Evaluation Criteria in Solid Tumors, there was no significant difference between both groups. CONCLUSIONS: Cystone can protect cancer patients from cisplatin nephrotoxicity without interfering with its antitumor activity.