Hilmi Orhan

Paracetamol (PAR) overdose is a major cause of drug-induced liver injury and is also associated with renal toxicity, both involving mitochondrial dysfunction and oxidative stress. This study investigated the dose- and organ-specific effects of the mitochondria-targeted antioxidant MitoTempo (MT) on PAR-induced hepatorenal toxicity in mice. Male C57BL/6J mice received a single toxic dose of PAR (600 mg/kg), either alone or combined with MT (20 or 40 mg/kg). Twenty-four hours after treatment, serum markers of liver and kidney injury were measured, and mitochondrial function was assessed in both organs. PAR administration caused severe liver injury and moderate renal dysfunction, accompanied by increased mitochondrial oxidative stress, glutathione imbalance, mitochondrial permeability transition pore opening, and disruption of electron transport chain (ETC) integrity. MT co-treatment attenuated several PAR-induced mitochondrial alterations in a dose- and tissue-dependent manner; however, MT did not consistently confer protection and, in some settings, exacerbated oxidative stress and bioenergetic dysfunction, particularly in the kidney. Notably, recovery of ETC protein levels by MT was not consistently associated with restoration of enzymatic activity. Overall, these findings demonstrate that MT exerts dual, dose- and organ-specific effects on PAR-induced mitochondrial dysfunction, highlighting that mitochondria-targeted antioxidants are not universally protective.

Purpose: Persistent organic pollutants (POPs) are lipophilic environmental contaminants with carcinogenic potential, yet data on their accumulation in human gastric tissue are limited. This study aimed to comprehensively quantify 32 POPs in malignant and non-malignant gastric tissues and to evaluate their distribution across blood and omental adipose tissue, together with metabolic enzyme activity, genetic polymorphisms, and oxidative damage markers. Methods: POP concentrations were measured in gastric tissue, blood, and omental adipose tissue from stomach cancer patients and controls undergoing stomach reduction surgery. Associations were evaluated using multivariable models adjusted for age, sex, and smoking. False discovery rate (FDR) correction was applied to account for multiple testing. Genotyping of CYP1A1, GSTP1, GSTM1, GSTT1, and OGG1 was performed, and CYP1A1 enzyme activity and urinary oxidative damage biomarkers were assessed. Results: The most robust differences were observed in gastric tissue, where 13 individual POPs and selected chemical classes remained significantly different between cancer and control groups after FDR correction. In blood, five individual POPs remained significant after correction. Several cross-compartment correlations persisted following FDR adjustment, particularly for selected HCH isomers and 4,4′-DDE. CYP1A1 activity did not differ between groups. Among oxidative biomarkers, only urinary o,o′-dityrosine remained significantly lower in cancer patients after FDR correction. In adjusted genetic models, no polymorphism demonstrated a statistically robust association in the overall analysis; the GSTP1 estimate was elevated but imprecise. Conclusion: Direct quantification of POPs in gastric tissue revealed selective accumulation patterns associated with stomach cancer. While systemic distribution and genetic variability may influence susceptibility, tissue-level POP differences represented the most consistent findings. Larger prospective studies are warranted to clarify temporal and mechanistic relationships.

Time-dependent cytosolic and mitochondrial alterations in non-cancerous and cancerous lung cells exposed to 5 Gy ionizing radiation were monitored over five days. Oxidative stress increased more rapidly in cancerous cells, affecting both compartments. In cancerous mitochondria, GSH levels decreased, while cytosolic GSH increased post-radiation. In contrast, non-cancerous mitochondria exhibited a transient GSH increase. Malondialdehyde levels rose in non-cancerous cells but declined in cancerous mitochondria. Basal ATP levels were higher in the cytosol of non-cancerous cells, while mitochondrial ATP remained comparable. Superoxide dismutase and glutathione peroxidase activities increased in non-cancerous cells, whereas catalase decreased in non-cancerous and increased in cancerous cells. Mitochondrial membrane potential, permeability transition pore integrity, and mitochondrial mass were significantly impaired in cancerous cells. Apoptotic markers were absent in non-cancerous cells except for Bax translocation on day 3. In cancerous mitochondria, cytochrome c and apoptosis-inducing factor peaked on days 1 and 5 but dropped on day 3, accompanied by a marked caspase-3 increase. ETC complexes showed significant radiation-induced alterations at protein, activity, and mRNA levels, differing between cell types. These findings highlight that mitochondrial oxidative stress is induced, enzymatic antioxidant defenses are weakened, apoptotic pathways are activated, and ETC complex activities are less responsive to radiation in cancerous cells compared to non-cancerous cells.

The need to create safe materials for biomedical and pharmaceutical applications has become a significant driving force for the development of new systems. Therefore, a chitosan-coated copolymer of itaconic acid, acrylic acid, and N-vinyl caprolactam (IT-AA-NVC) was prepared by radical polymerization and subsequent coating via nanoprecipitation to give a system capable of sustained delivery of melatonin. Although melatonin brings undoubted benefits to the human body, aspects of the optimal dose, route, and time of administration for the obtaining of suitable treatment outcomes remain under discussion. The entrapment of melatonin in biocompatible polymeric systems can prevent its oxidation, decrease its toxicity, and provide an increased half-life, resulting in an enhanced pharmacokinetic profile with improved patient compliance. The structures of the biopolymer and conjugate were proven by FTIR, thermal properties were tested by DSC, and the morphologies were followed by SEM. The loading efficiency and in vitro release profile were studied by means of HPLC, and a delayed release profile with an initial burst was obtained. The potential systemic toxicity of the formulation was studied in vivo; a mild hepatotoxicity was observed following administration of the melatonin-loaded formulation to mice, both by histopathology and blood clinical biochemistry. Histopathology showed a mild nephrotoxicity as well; however, kidney clinical biochemistry did not support this.

Background: CHO-K1 cells were used as in vitro model to explore mechanisms of cytotoxi-city of the test drugs. Aim: To provide in vitro data on toxicity mechanisms of clozapine, diclofenac and nifedipine. Objective: Cytotoxic mechanisms of clozapine (CLZ), diclofenac (DIC) and nifedipine (NIF) were studied in CHO-K1 cells in vitro. All three drugs induce adverse reactions in some patients with partially unknown mechanisms Methods: Following the determination of time- and dose-dependency of cytotoxicity by the MTT test, cytoplasmic membrane integrity was explored by the LDH leakage test. Both end-points were further examined in the presence of soft and hard nucleophilic agents, glutathione (GSH) and potassium cyanide (KCN), respectively, and either individual or general cytochrome P450 (CYP) inhibitors, whether CYP-catalysed formation of electrophilic metabolites play a role in the observed cytotoxicity and membrane damage. The generation of reactive metabolites during the incubations was also explored. Formation of malondialdehyde (MDA) and oxidation of dihydrofluorescein (DCFH) were monitored whether peroxidative membrane damage and oxidative stress take place in cytotoxicity. Incubations were also conducted in the presence of chelating agents of EDTA or DTPA to explore any possible role of metals in cytotoxicity by facilitating electron transfer in redox reactions. Finally, mitochondrial membrane oxidative degradation and permeability transition pore (mPTP) induction by the drugs were tested as markers of mitochondrial damage. Results: The presence of an individual or combined nucleophilic agents significantly diminished CLZ- and NIF-induced cytotoxicities, while the presence of both agents paradoxically increased DIC-induced cytotoxicity by a factor of three with the reason remaining unknown. The presence of GSH significantly increased DIC-induced membrane damage too. Prevention of membrane damage by the hard nucleophile KCN suggests the generation of a hard electrophile upon DIC and GSH interaction. The presence of CYP2C9 inhibitor sulfaphenazole significantly diminished DIC-induced cytotoxicity, probably by preventing the formation of 4-hydroxylated metabolite of DIC, which further converts to an electrophilic reactive intermediate. Among the chelating agents, EDTA caused a marginal decrease in CLZ-induced cytotoxicity, while DIC-induced cytotoxicity was amplified by a factor of five. Both reactive and stable metabolites of CLZ could be detected in the incubation medium of CLZ with CHO-K1 cells, which are known to have low metabolic capacity. All three drugs caused a significant increase in cytoplasmic oxidative stress by means of DCFH oxidation, which was confirmed by increased MDA from cytoplasmic as well as mitochondrial membranes. The addition of GSH paradoxically and significantly increased DIC-induced MDA formation, in parallel with the increase in membrane damage when DIC and GSH combined. Conclusion: Our results suggested that the soft electrophilic nitrenium ion of CLZ is not responsible for the observed in vitro toxicities, and this may originate from a relatively low amount of the metabolite due to the low metabolic capacity of CHO-K1. A hard electrophilic intermediate may contribute to cellular membrane damage incubated with DIC, while a soft electrophilic intermediate seems to exacerbate cell death by a mechanism other than membrane damage. A significant decrease in cytotoxicity of NIF by GSH and KCN suggested that both soft and hard electrophiles contribute to NIF-induced cytotoxicity. All three drugs induced peroxidative cytoplasmic membrane damage, while only DIC and NIF induced peroxidative mitochondrial membrane damage, which suggested mitochondrial processes may contribute to adverse effects of these drugs in vivo.