Effects of Antiarrhythmic Drugs on Apoptotic Pathways in H9c2 Cardiac Cells

Cardiotoxicity and ROS Protection Assessment of three Structure-Related N-Acylhydrazones with Potential for the Treatment of Neurodegenerative Diseases

The senescence process is associated with accumulated oxidative damage and increased metal concentration in the heart and brain. Besides, abnormal metal-protein interactions have also been linked with the development of several conditions, including Alzheimer's and Parkinson's diseases. Over the years we have described a series of structure-related compounds with different activities towards models of such diseases. In this work, we evaluated the potential of three N-acylhydrazones (INHHQ: 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone, HPCIH: pyridine-2-carboxaldehyde isonicotinoyl hydrazone and X1INH: 1-methyl-1H-imidazole-2-carboxaldehyde isonicotinoyl hydrazone) to prevent oxidative stress in cellular models, with the dual intent of being active on this pathway and also to confirm their lack of cardiotoxicity as an important step in the drug development process, especially considering that the target population often presents cardiovascular comorbidity. The 8-hydroxyquinoline-contaning compound, INHHQ, exhibits a significant cardioprotective effect against hydrogen peroxide and a robust antioxidant activity. However, this compound is the most toxic to the studied cell models and seems to induce oxidative damage on its own. Interestingly, although not possessing a phenol group in its structure, the new-generation 1-methylimidazole derivative X1INH showed a cardioprotective tendency towards H9c2 cells, demonstrating the importance of attaining a compromise between activity and intrinsic cytotoxicity when developing a drug candidate.

Effects of chronic amiodarone treatment on rat testis

Amiodarone is a potent agent used to treat tachyarrhythmias, which are especially refractory to other medications, in both adults and children. Although widely used as an antiarrhythmic drug, amiodarone causes many serious adverse effects that limit its use. This study investigated the possible morphological and apoptotic effects of amiodarone on rat testes. Amiodarone was administered to male Sprague-Dawley rats at doses of 20 or 200mg/kg/day for 14 days. A histopathological examination of testicular tissue revealed the presence of inflammatory cells in the seminiferous tubule lumen together with swelling and vacuolization in the cytoplasm of some spermatogonia; these effects occured in a dose-dependent manner. Immunohistochemical staining showed evidence of apoptosis, including caspase-3, caspase-9, Bax and increased DNA fragmentation was detected via a terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. In conclusion, the results show that chronic amiodarone treatment causes dose-dependent degenerative and apoptotic effects on rat testes.

Ameliorative effect of grapefruit juice on amiodarone-induced cytogenetic and testicular damage in albino rats

OBJECTIVE

To evaluate the ameliorative role of grapefruit juice on the cytogenetic and testicular damage induced by the antiarrythmic drug amiodarone in albino rats.

METHODS

Animals were divided into four groups. Group I was considered as control. Group II was given grapefruit juice at a dose level of 27 mL/kg body weight. Group III was orally administered amiodarone (18 mg/kg body weight) daily for 5 weeks. Animals were sacrificed after 5 weeks of treatment. Bone marrow was collected from the femurs for analysis of chromosomal aberrations and mitotic indices. Testes were removed and stained with H&E for histological examination. Sperms were collected from epidedymis for detection of sperm head abnormalities. Comet assay was used to detect DNA damage.

RESULTS

Amiodarone treatment caused a significant increase in the percentage of chromosomal aberrations, decreased the mitotic index and increased DNA damage. The testis showed many histopathological alterations, inhibition of spermatogenesis and morphometric changes. The number of sperm head abnormalities was increased. Treating animals with amiodarone and grapefruit juice caused a reduction in chromosomal aberrations, mitotic index, DNA damage and testicular alterations caused by amiodarone.

CONCLUSIONS

The results of this study indicated that grapefruit juice ameliorates the cytotoxicty and testicular alterations induced by amiodarone in albino rats and this is may be due to the potent antioxidant effects of its components.

Effect of grapefruit juice on amiodarone induced nephrotoxicity in albino rats

Amiodarone is a potent antiarrhythmic drug that is used to treat ventricular and supraventricular tachyarrhythmias. The present work studied the effect of amiodarone on the kidney of albino rats and the possible ameliorative role of grapefruit juice. Administration of amiodarone by gastric intubation (18 mg/kg body weight (b.w.), daily for 5 weeks) caused many histological alterations including intertubular leucocytic infiltrations, degeneration of the renal tubules, and atrophy of the glomeruli. Amiodarone caused marked elevation in serum creatinine and blood urea nitrogen. Histochemical examination of the renal tubules revealed depletion of glycogen and total proteins. Besides, animals administered with amiodarone showed an increase of apoptotic bands as detected by gel electrophoresis. Treating animals with amiodarone and grapefruit juice (27 ml/kg b.w.) caused an improvement in histological and histochemical appearance of the kidney together with decrease of serum creatinine and blood urea nitrogen. Moreover, the apoptosis was decreased. It is concluded from the obtained results that grapefruit juice ameliorates the nephrotoxicity of amiodarone in albino rats and this may be due to the potent antioxidant effects of its components.

Window current through the T-type Ca2+ channel triggers the mechanism for cellular apoptosis via mitochondrial pathways

We hypothesized that Ca(2+) entry through the window T-type Ca(2+) current causes apoptosis. To test this hypothesis, we transfected human embryonic kidney (HEK) 293 cells to express recombinant Cav3.2 T-type Ca(2+) channels (hereafter called HEK-Cav3.2 cells). After incubation in media containing a high concentration (7.2 mM) of Ca(2+), intracellular Ca(2+) levels increased in HEK-Cav3.2 cells without electrical stimulation but not in untransfected HEK293 cells. In quiescent HEK-Cav3.2 cells exposed to high Ca(2+) media, apoptosis, as indicated by the appearance of hypodiploid cells, loss of mitochondrial transmembrane potential, and activation of caspases-3 and -9 was observed, while caspase-8 was not activated. These apoptosis-associated changes were blunted by pretreatment with the R(-)-isomer of efonidipine, a selective blocker of T-type Ca(2+) channels. High Ca(2+) did not induce apoptosis in untransfected HEK293 cells. Our findings show that Ca(2+) entry through the steady-state window current of T-type Ca(2+) channels causes apoptosis via mitochondrial pathways, and suggests that T-type Ca(2+) channels may be novel therapeutic targets for several diseases associated with abnormal apoptosis.

Tumor necrosis factor-alpha potentiates the cytotoxicity of amiodarone in Hepa1c1c7 cells: roles of caspase activation and oxidative stress

Amiodarone (AMD), a class III antiarrhythmic drug, causes idiosyncratic hepatotoxicity in human patients. We demonstrated previously that tumor necrosis factor-alpha (TNF-α) plays an important role in a rat model of AMD-induced hepatotoxicity under inflammatory stress. In this study, we developed a model in vitro to study the roles of caspase activation and oxidative stress in TNF potentiation of AMD cytotoxicity. AMD caused cell death in Hepa1c1c7 cells, and TNF cotreatment potentiated its toxicity. Activation of caspases 9 and 3/7 was observed in AMD/TNF-cotreated cells, and caspase inhibitors provided minor protection from cytotoxicity. Intracellular reactive oxygen species (ROS) generation and lipid peroxidation were observed after treatment with AMD and were further elevated by TNF cotreatment. Adding water-soluble antioxidants (trolox, N-acetylcysteine, glutathione, or ascorbate) produced only minor attenuation of AMD/TNF-induced cytotoxicity and did not influence the effect of AMD alone. On the other hand, α-tocopherol (TOCO), which reduced lipid peroxidation and ROS generation, prevented AMD toxicity and caused pronounced reduction in cytotoxicity from AMD/TNF cotreatment. α-TOCO plus a pancaspase inhibitor completely abolished AMD/TNF-induced cytotoxicity. In summary, activation of caspases and oxidative stress were observed after AMD/TNF cotreatment, and caspase inhibitors and a lipid-soluble free-radical scavenger attenuated AMD/TNF-induced cytotoxicity.

The effect of vitamin C on amiodarone-induced toxicity in rat thymocytes

Although, the antiarrhythmic effect of amiodarone (AMD) is well characterized, the mechanism of its toxicity on extracardiac tissues is still poorly understood. Several antioxidants have been shown to prevent AMD-induced toxicity by antioxidant and/or non-antioxidant mechanisms. In the current study, we evaluated the possible protective effect, in vitro, of vitamin C on AMD-induced toxicity in rat thymocytes. Rat thymocytes were cultured with increasing AMD concentrations (1–20 μM) with or without vitamin C (1000 μg/ml), for 24 hours. Cells treatment with AMD resulted in a concentration-dependent increase of hypodiploid cells and a significant decrease in cellular glutathione content. Vitamin C combined with AMD significantly decreased the proportion of hypodiploid cells and markedly increased the cellular glutathione content, compared with AMD treatment alone. These results suggest that treatment with vitamin C may prevent AMD-induced toxicity in rat thymocytes by restoring cellular glutathione content.

Oxidative modulation of marcaine and lekoptin in H9C2 rat myoblasts

AIM

The cytotoxicity of marcaine was estimated in combination with a calcium channel blocker. In addition, the influence of marcaine and marcaine plus lekoptin on a model system using the H9C2 cardiac cell line was investigated.

METHODS

Cells were incubated for five hours with marcaine, lekoptin, or with both drugs simultaneously. Apoptotic cells were detected using the TUNEL assay and the alkaline comet assay. Mitochondrial cell function after drug uptake was examined using the MTT assay. The concentration of MDA (malondialdehyde) -- the final product of fatty-acid peroxidation, was quantified spectrophotometrically. The expression of glutathione S-transferase pi (GST-pi) was detected by immunofluorescence (IF) and Western blotting (WB) and inducible nitric oxide synthase (iNOS) was assessed by immunocytochemical staining (ABC).

RESULTS

Incubation with marcaine resulted in the highest number of apoptotic cells. After incubation with both marcaine and lekoptin, moderate damage to cells (54.2%+/-1.775% of DNA destruction) was observed. The highest levels of iNOS and GST-pi expression were observed in cells treated with marcaine and marcaine plus lekoptin. The characteristic nuclear GST-pi expression was observed in cells treated with both drugs.

CONCLUSION

Lekoptin stimulated cells to proliferate. Marcaine caused membrane damage and ultimately cell death.

Stimulation of erythrocyte cell membrane scrambling by amiodarone

Side effects of amiodarone, an effective antiarrhythmic drug, include anemia, which may be caused by decreased formation or accelerated death of erythrocytes. Suicidal erythrocyte death (eryptosis) is characterized by cell shrinkage and cell membrane scrambling leading to phosphatidylserine exposure at the cell surface. Stimulators of erythrocyte membrane scrambling include increase of cytosolic Ca2+ concentration ([Ca2+]i) following activation of Ca2+-permeable cation channels. Moreover, eryptosis is triggered by ceramide. The present study has been performed to test for an effect of amiodarone on eryptosis. Erythrocytes from healthy volunteers were exposed to amiodarone and phosphatidylserine exposure (annexin V binding), cell volume (forward scatter), [Ca2+]i (Fluo3-dependent fluorescence), and ceramide formation (anti-ceramide-FITC antibody and radioactive labelling) determined by flow cytometry. Exposure of erythrocytes to amiodarone (1 microM) increased [Ca2+]i and triggered annexin V binding, but did not significantly decrease forward scatter and did not significantly influence ceramide formation. Amiodarone augmented the increase of annexin binding following hypertonic shock (addition of 550 mM sucrose) but did not significantly alter the enhanced annexin binding following Cl- removal (replacement with gluconate). Amiodarone did not significantly modify the decrease of forward scatter following hypertonic shock or Cl- removal. The present observations disclose a novel action of amiodarone which may contribute to the side effects of the drug.