Modification of CYP2E1 and CYP3A4 activities in haemoglobin E-beta thalassemia patients

Population pharmacokinetics of cyclosporine A in pediatric patients with thalassemia undergoing allogeneic hematopoietic stem cell transplantation

PURPOSE

To establish the population pharmacokinetics (PPK) model of cyclosporine A(CsA) in pediatric patients with thalassemia undergoing allogeneic hematopoietic stem cell transplantation (HSCT), aiming at providing a reference for clinical dose individualization of CsA.

METHODS

Children with thalassemia who underwent allogeneic HSCT were enrolled retrospectively. The PPK structural model and the random variable model of CsA were established on NONMEN. And goodness of fit plots (GOFs), visual predictive check (VPC), and bootstrap and normalized prediction distribution errors (NPDE) were used to evaluate the final model.

RESULTS

A one-compartment model with first-order absorption was employed to fit the base model. A total of 74 pediatric patients and 600 observations of whole blood concentration were included. The final model included weight (WT) in clearance (CL), alongside post-operative day (POD), fluconazole (FLUC), voriconazole (VORI), posaconazole (POSA), and red blood cell count (RBC) significantly. All the model evaluations were passed.

CONCLUSION

In the PPK model based on the pediatric cohort on CsA with thalassemia undergoing allogeneic HSCT, WT, POD, FLUC, VORI, POSA, and RBC were found to be the significant factors influencing CL of CsA. The reliability and robustness of the final model were excellent. It is expected that the PPK model can assist in individualizing dosing strategy clinically.

The Effects of Chronic Iron Overload in Rats with Acute Acetaminophen Overdose

BACKGROUND AND AIMS

Rats are resistant to acetaminophen (APAP) hepatotoxicity. In this study, we evaluated whether by augmentation of the hepatic oxidative stress, through the induction of hepatic iron overload (IO), it will be feasible to overcome the resistance of rats to the toxic effects of APAP.

METHOD

Rats with no or increased hepatic IO.

RESULTS

Providing iron by diet induced hepatocellular IO, while parenteral iron administration induced combined hepatocellular and sinusoidal cell IO. APAP administration to rats with no IO caused an increase in hepatic oxidative stress and a decrease in the hepatic antioxidative markers but no hepatic cell damage. APAP administration to rats with hepatocellular IO further amplified the hepatic oxidative stress but induced only hepatocyte feathery degeneration without any increase in serum aminotransaminases. APAP administration to rats with combined hepatocellular and sinusoidal cell IO caused an unexpected decrease in hepatic oxidative stress and increase in the hepatic antioxidative markers and no hepatic cell damage. No hepatic expression of activated c-jun-N-terminal kinase was detected in any of the rats.

CONCLUSIONS

The hepatic distribution of iron may affect its oxidative/antioxidative milieu. Augmentation of hepatic oxidative stress did not increase the rats' vulnerability to APAP.

Mamao Pomace Extract Alleviates Hypertension and Oxidative Stress in Nitric Oxide Deficient Rats

Reactive oxygen species (ROS)-induced oxidative stress plays a major role in pathogenesis of hypertension. Antidesma thwaitesianum (local name: Mamao) is a tropical plant distributed in the tropical/subtropical areas of the world, including Thailand. Mamao pomace (MP), a by-product generated from Mamao fruits, contains large amounts of antioxidant polyphenolic compounds. The aim of this study was to investigate the antihypertensive and antioxidative effects of MP using hypertensive rats. For this purpose, male Sprague-Dawley rats were given Nω-nitro-L-arginine methyl ester (L-NAME), an inhibitor of endothelial nitric oxide synthase (eNOS), in drinking water (50 mg/kg) for three weeks. MP extract was orally administered daily at doses of 100 and 300 mg/kg. L-NAME administration induced marked increase in blood pressure, peripheral vascular resistance, and oxidative stress. MP treatment significantly prevented the increase in blood pressure, hindlimb blood flow and hindlimb vascular resistance of L-NAME treated hypertensive rats (p < 0.05). The antihypertensive effect of MP treatment was associated with suppression of superoxide production from carotid strips and also with an increase in eNOS protein expression and nitric oxide bioavailability. The present results provide evidence for the antihypertensive effect of MP and suggest that MP might be useful as a dietary supplement against hypertension.

Curcumin protects against cadmium-induced vascular dysfunction, hypertension and tissue cadmium accumulation in mice

Curcumin from turmeric is commonly used worldwide as a spice and has been demonstrated to possess various biological activities. This study investigated the protective effect of curcumin on a mouse model of cadmium (Cd)—induced hypertension, vascular dysfunction and oxidative stress. Male ICR mice were exposed to Cd (100 mg/L) in drinking water for eight weeks. Curcumin (50 or 100 mg/kg) was intragastrically administered in mice every other day concurrently with Cd. Cd induced hypertension and impaired vascular responses to phenylephrine, acetylcholine and sodium nitroprusside. Curcumin reduced the toxic effects of Cd and protected vascular dysfunction by increasing vascular responsiveness and normalizing the blood pressure levels. The vascular protective effect of curcumin in Cd exposed mice is associated with up-regulation of endothelial nitric oxide synthase (eNOS) protein, restoration of glutathione redox ratio and alleviation of oxidative stress as indicated by decreasing superoxide production in the aortic tissues and reducing plasma malondialdehyde, plasma protein carbonyls, and urinary nitrate/nitrite levels. Curcumin also decreased Cd accumulation in the blood and various organs of Cd-intoxicated mice. These findings suggest that curcumin, due to its antioxidant and chelating properties, is a promising protective agent against hypertension and vascular dysfunction induced by Cd.

Preventive and therapeutic effects of quercetin on lipopolysaccharide-induced oxidative stress and vascular dysfunction in mice

Quercetin, a dietary antioxidant flavonoid, possesses strong anti-inflammatory and cytoprotective activities. The effects were investigated in an animal model of lipopolysaccharide (LPS)-induced endotoxaemia and vascular dysfunction in vivo. Male ICR mice were injected with LPS (10 mg/kg; i.p.). Quercetin (50 or 100 mg/kg) was intragastrically administered either before or after LPS administration. Fifteen hours after LPS injection, mice were found in endotoxaemic condition, as manifested by hypotension, tachycardia, and blunted vascular responses to vasodilators and vasoconstrictor. The symptoms were accompanied by increased aortic iNOS protein expression, decreased aortic eNOS protein expression, marked suppression of cellular glutathione (GSH) redox status, enhanced aortic superoxide production, increased plasma malodialdehyde and protein carbonyl, and elevated urinary nitrate/nitrite. Treatment with quercetin either before or after LPS preserved the vascular function, as blood pressure, heart rate, vascular responsiveness were restored to near normal values, particularly when quercetin was given as a preventive regimen. The vascular protective effects were associated with upregulation of eNOS expression, reduction of oxidative stress, and maintained blood GSH redox ratio. Overall findings suggest the beneficial effect of quercetin on the prevention and restoration of a failing eNOS system and alleviation of oxidative stress and vascular dysfunction against endotoxin-induced shock in mice.

Altered vascular function, arterial stiffness, and antioxidant gene responses in pediatric thalassemia patients

Patients with thalassemia major are susceptible to cardiovascular complications by mechanisms not fully understood. Although overt cardiovascular complications usually occur after puberty, their underlying pathogenesis may begin much earlier. This study investigated whether there were early changes in vascular endothelial function and arterial stiffness in young patients with beta-thalassemia and hemoglobin E, and whether these changes were associated with oxidative stress and expression of antioxidant genes. The study recruited 30 pediatric patients and 30 age-matched control subjects. Compared with the control subjects, the patients had increased levels of oxidant biomarkers including malondialdehyde, protein carbonyl, and non-transferrin-bound iron and a decreased glutathione redox ratio. There were clear signs of vascular endothelial dysfunction and increased arterial stiffness, as shown by marked suppression of forearm blood flow after reactive hyperemia and increased pulse-wave velocity in the trunk and legs. The changes in FBF were associated with oxidative stress markers and free iron. An adaptive antioxidant gene response was activated in blood mononuclear cells, as shown by upregulation of GCLC and Bach-1 mRNA but downregulation of heme oxygenase-1 and thioredoxin mRNA. The results highlight the vascular changes seen even in young patients during treatment. These changes were associated with oxidative stress and suggest an adaptive response that serves to protect host cells from further oxidative damage.

Dicoumarol enhances gemcitabine-induced cytotoxicity in high NQO1-expressing cholangiocarcinoma cells

AIM: To investigate whether dicoumarol, a potent inhibitor of NAD(P)H quinone oxidoreductase-1 (NQO1), potentiates gemcitabine to induce cytotoxicity in cholangiocarcinoma cells (CCA) and the role of reactive oxygen generation in sensitizing the cells.

METHODS: Four human cell lines with different NQO1 activity were used; the human CCA cell lines, KKU-100, KKU-OCA17, KKU-M214, and Chang liver cells. NQO1 activity and mRNA expression were determined. The cells were pretreated with dicoumarol at relevant concentrations before treatment with gemcitabine. Cytotoxicity was determined by staining with fluorescent dyes. Oxidant formation was examined by assay of cellular glutathione levels and reactive oxygen species production by using dihydrofluorescein diacetate. Measurement of mitochondrial transmembrane potential was performed by using JC-1 fluorescent probe. Western blotting analysis was performed to determine levels of survival related proteins.

RESULTS: Dicoumarol markedly enhanced the cytotoxicity of gemcitabine in KKU-100 and KKU-OCA17, the high NQO1 activity and mRNA expressing cells, but not in the other cells with low NQO1 activity. Dicoumarol induced a marked decrease in cellular redox of glutathione in KKU-100 cells, in contrast to KKU-M214 cells. Dicoumarol at concentrations that inhibited NQO1 activity did not alter mitochondrial transmembrane potential and production of reactive oxygen species. Gemcitabine alone induced activation of NF-κB and Bcl-_XL protein expression. However, gemcitabine and dicoumarol combination induced increased p53 and decreased Bcl-_XL levels in KKU-100, but not in KKU-M214 cells.

CONCLUSION: NQO1 may be important in sensitizing cells to anticancer drugs and inhibition of NQO1 may be a strategy for the treatment of CCA.

Endothelial dysfunction and oxidant status in pediatric patients with hemoglobin E-beta thalassemia

Thalassemia major is characterized by anemia, iron overload, and oxidant damage to major organs, especially the cardiovascular system. Oxidative stress is ultimately involved in endothelial dysfunction, a condition which is evident in adults suffering from various cardiovascular diseases including thalassemia. We investigated endothelial function in pediatric patients with hemoglobin E-beta thalassemia (HbE-beta thalassemia), who have been exposed to excessive iron and oxidative stress for much shorter period than adults with thalassemia. We recruited 22 blood transfusion-dependent HbE-beta thalassemia patients aged 11.8 +/- 2.9 years and 20 healthy controls aged 12.1 +/- 1.7 years. Oxidant status was determined, and endothelial function was assessed by a forearm blood flow technique. Oxidative stress was increased in the thalassemic patients, as blood glutathione (GSH) and ratios of reduced GSH to GSH disulfide were markedly reduced, and superoxide anion released from blood cells was highly elevated. Oxidative stress response, assessed by gamma-glutamylcysteine ligase activity, was increased approximately twofold in thalassemia patients. Basal forearm blood flow was significantly increased in patients compared with controls (7.3 +/- 1.8 vs 6.0 +/- 1.8 ml/100 ml tissue/min, respectively), whereas forearm vasodilatory response to reactive hyperemia was depressed by 50% in patients compared with controls. Endothelial function is impaired in young thalassemia patients, and impaired endothelial function is associated with oxidant stress.

Inflammatory cytokines suppress arylamine N-acetyltransferase 1 in cholangiocarcinoma cells

AIM: To evaluate the effect of inflammatory cytokines on arylamine N-acetyltransferase 1 (NAT1), which is a phase-II enzyme involved in the biotransformation of aromatic and heterocyclic amines found in food, drugs and the environment.

METHODS: Human cholangiocarcinoma KKU-100 cells were treated with a mixture of proinflammatory cytokines (interferon-γ, interleukin-1β, and tumor necrosis factor-α) for 48 h, and the effect on NAT1 activity was assessed by high performance liquid chromatography, while NAT1 expression was determined by reverse-transcription polymerase chain reaction. The oxidative stress on the cells was examined by the formation of nitric oxide, superoxide anion and glutathione (GSH) levels. The cells were also treated with S-nitroso-glutathione (GSNO), a nitric oxide donor, to see if the responses were similar to those obtained with the inflammatory cytokines.

RESULTS: Cytokines suppressed NAT1 activity, reducing the V_max without affecting the K_m. Cytokines also had a significant impact on the induction of nitric oxide production and in reducing the redox ratios of glutathione (GSH) and GSH disulfide. Treatment with GSNO for 2-48 h reduced NAT1 activity without affecting the GSH ratio. Moreover, inflammatory cytokines and GSNO suppressed NAT1 mRNA expression.

CONCLUSION: These findings indicate an association between inflammation and suppression of NAT1, which perhaps contributes to chemical-mediated toxicity and carcinogenesis.