Prevention of doxorubicin-induced damage to rat heart myocytes by arginine analog nitric oxide synthase inhibitors and their enantiomers

Extra arginine supplementation during the suckling period alleviates weaning stress through the regulation of dendritic cells and Notch2 signaling in piglets

This study aims to study the effects of extra arginine (Arg) supplementation during the suckling period on the weaning stress and intestinal barrier function of breastfed piglets. Forty 7-day-old breastfed piglets divided into the control group (CON) and Arg group (Arg) were fed with extra saline or Arg (250 mg per kg per d body weight), respectively. All piglets were weaned when they were 21 days old. Eight piglets from each group were sacrificed before weaning and on the 3rd-day after weaning, respectively. The results showed that Arg improved the average daily weight gain of piglets before weaning (P < 0.01) and decreased the average daily weight loss after weaning (P < 0.05). Weaning decreased the ratio of the villus length versus crypt depth (V/C) in the SI (P < 0.001), while Arg increased the V/C of the jejunum (P < 0.05). Arg increased the levels of immunoglobulins in the serum and SI (P < 0.05), decreased pro-inflammatory cytokines and increased anti-inflammatory cytokines in the SI (P < 0.05). In addition, Arg supplementation increased the numbers of SWC3a⁺CD40⁺ (P < 0.01) and SWC3a⁺SLAII⁺ DCs (P < 0.05), down-regulated Notch2 expression and up-regulated Jagged1 expression in the ilea of weaning piglets (P < 0.05). In conclusion, Arg supplementation during the suckling period decreased the LDH leakage in the SI, improved the intestinal morphology, down-regulated the contents of pro-inflammatory cytokines, accelerated the accumulation of DC precursors before weaning and increased the number of mature DCs after weaning, and thus improved the growth performance and reduced the weaning stress of piglets, and this might be associated with the regulation of Notch2 signaling.

Vitamin C: historical perspectives and heart failure

Vitamin C (Vit C) is an ideal antioxidant as it is easily available, water soluble, very potent, least toxic, regenerates other antioxidants particularly Vit E, and acts as a cofactor for different enzymes. It has received much attention due to its ability in limiting reactive oxygen species, oxidative stress, and nitrosative stress, as well as it helps to maintain some of the normal metabolic functions of the cell. However, over 140 clinical trials using Vit C in different pathological conditions such as myocardial infarction, gastritis, diabetes, hypertension, stroke, and cancer have yielded inconsistent results. Such a divergence calls for new strategies to establish practical significance of Vit C in heart failure or even in its prevention. For a better understanding of Vit C functioning, it is important to revisit its transport across the cell membrane and subcellular interactions. In this review, we have highlighted some historical details of Vit C and its transporters in the heart with a particular focus on heart failure in cancer chemotherapy.

The role of nitric oxide in Doxorubicin-induced cardiotoxicity: experimental study

Objective: We evaluated the myocardial damage in rats treated with doxorubicin (DOX) alone and in combination with nitric oxide synthase (NOS) inhibitors.

Materials and Methods: Twenty-four male Sprague Dawley rats (12 weeks old, weighing 262±18 g) were randomly assigned into 4 groups (n=6). Group I was the control group. In Group II, rats were treated with intraperitoneal (ip) injections of 3 mg/kg DOX once a week for 5 weeks. In Group III, rats received weekly ip injections of 30 mg/kg L-NAME (nonspecific NOS inhibitor) 30 min before DOX injections for 5 weeks. In Group IV, rats received weekly ip injections of 3 mg/kg L-NIL (inducible NOS inhibitor) 30 min before DOX injections for 5 weeks. Rats were weighed 2 times a week. At the end of 6 weeks, hearts were excised and then fixed for light and electron microscopy evaluation and tissue lipid peroxidation (malondialdehyde). Blood samples were also obtained for measuring plasma lipid peroxidation.

Results: Weight loss was observed in Group II, Group III, and Group IV. Weight loss was statistically significant in the DOX group. Findings of myocardial damage were significantly higher in animals treated with DOX only than in the control group. Histopathological findings of cardiotoxicity in rats treated with DOX in combination with L-NAME and L-NIL were not significantly different compared with the control group. The level of plasma malondialdehyde in the DOX group (9.3±3.4 µmol/L) was higher than those of all other groups.

Conclusion: Our results showed that DOX cardiotoxicity was significantly decreased when DOX was given with NO synthase inhibitors.

FGF-2 protects cardiomyocytes from doxorubicin damage via protein kinase C-dependent effects on efflux transporters

AIMS

The anti-cancer anthracycline doxorubicin (DOX) increases the risk of cardiac damage, indicating a need to protect the heart and still allow the benefits of drug treatment. Fibroblast growth factor-2 (FGF-2) is cardioprotective against ischaemia-reperfusion injury. Our aim is to investigate: (i) the ability of FGF-2 to protect against DOX-induced cardiomyocyte damage and (ii) the contribution of efflux drug transport to any increase in injury-resistance.

METHODS AND RESULTS

Neonatal rat cardiomyocyte damage was assessed by measuring cell death markers and lactate dehydrogenase (LDH) activity in the culture medium. LDH activity was increased significantly after incubation with 0.5 μM DOX for 24 h in the absence but not presence of 10 nM FGF-2; this beneficial effect of FGF-2 was blocked by tyrosine kinase (FGF) receptor inhibition. An increase in efflux drug transporter RNA levels was also detected after FGF-2 treatment in the presence of DOX. The beneficial effect of FGF-2 against cell damage and increased transporter RNA levels were blunted with protein kinase C (PKC) inhibition. Finally, FGF-2 stimulated efflux transport of calcein and DOX, and treatment with efflux transporter inhibitors significantly attenuated the protective effect of FGF-2 from DOX-induced injury.

CONCLUSION

Administered FGF-2 increases resistance to DOX-induced cardiomyocyte damage, by a mechanism dependent on PKC as well as regulation of efflux transporter production and/or function.

The influence of oracin on reduction and toxicity of doxorubicin in hepatocytes and mammary epithelial cells MCF-10A

The ways, how to increase effectiveness of doxorubicin (DOX) in cancer cells and decrease its toxicity in normal cells, have been intensively studied. In breast cancer cells MCF-7, isoquinoline derivative oracin (ORC) inhibited DOX reduction and increased DOX antiproliferative effect. The aim of this study was to test the influence of ORC on the reduction of DOX and its toxicity in hepatocytes and non-tumourous breast cells. The kinetics of DOX reduction was measured in cytosols from rat liver, human liver and human mammary epithelial cells MCF-10A. Activity and expression of carbonyl reductase 1 (CBR1) were assayed using menadione as a substrate and western blot analysis. End-point tests of viability served for study of cytotoxicity of DOX, ORC and DOX+ORC combinations in rat hepatocytes and MCF-10A cells. The inhibitory effect of ORC on DOX reductases was almost none in MCF-10A cells and mild in liver. CBR1 expression and activity was lower in non-tumourous MCF-10A cells than in cancer MCF-7 cells. Cytotoxicity tests showed that DOX+ORC combinations had significantly lower toxicity than DOX alone in MCF-10A cells as well as in hepatocytes. ORC significantly decreases DOX toxicity in MCF-10A and in hepatocytes. Therefore, concomitant use of ORC and DOX may protect normal cells against DOX toxicity.

Nitric oxide: a new biomarker of Doxorubicin toxicity in children?

Doxorubicin (DOX) has been used in the treatment of childhood cancers, but its usage is limited because of cardiotoxicity. There are many studies on the role of nitric oxide (NO) in several cardiac diseases. However, to the authors' knowledge, no studies have investigated the plasma levels of total nitrite, a stable product of NO, in children that received DOX. The authors determined plasma total nitrite levels in 29 children who received DOX and investigated the correlations between these and other clinical and laboratory findings. All patients were in remission during the study period. Plasma total nitrite levels and cardiac functions were determined prospectively. The mean cumulative DOX dose was 310.0 ± 90.9 mg/m(2). In echocardiographic evaluation, 3 patients (10.3%) had a pathological value for ejection fraction (EF) and/or fractional shortening (FS), whereas 11 patients (37.9%) had a threshold value. Total nitrite levels were higher in patients than in matched controls (75.24 ± 39.4 vs 43.14 ± 10.58 μmol/L, respectively, P < .001). It was also found to be higher in patients who had a pathological/threshold value of EF and FS than in patients who had a physiological value of EF and FS (92.35 ± 50.36 vs 59.26 ± 13.56 μmol/L, respectively, P = .038). A negative correlation was found between FS and plasma total nitrite level (r = -.42, P = .023). The authors speculate that increased NO may be a sign of subclinical cardiotoxicity of DOX.

Endogenous production and exogenous exposure to nitric oxide augment doxorubicin cytotoxicity for breast cancer cells but not cardiac myoblasts

We studied the effect of nitric oxide (*NO) on the anticancer activity of doxorubicin. When MCF-7 human breast cancer cells were exposed to an aqueous solution of *NO delivered as a bolus 30 min prior to doxorubicin, the cytotoxic effect as measured in a clonogenic assay was increased (doxorubicin alone, 40% survival, doxorubicin plus *NO, 5% survival). The *NO donor diethylamine nitric oxide, but not inactivated donor, also yielded an increase in doxorubicin cytotoxicity. The sequence was important since the simultaneous application of *NO with doxorubicin yielded only a small augmentation of effect, and the exposure of the cells to doxorubicin prior to the *NO obliterated the augmentation. Prior depletion of glutathione by incubation of the cells for 24h with D,L-buthionine-S,R-sulfoximine (BSO) further increased the cytotoxicity so that BSO plus *NO plus doxorubicin killed all of the clones. MCF-7 cells transduced with inducible nitric oxide synthase gene (iNOS) through an adenoviral vector overexpressed iNOS and produced increased amounts of nitrite, an indicator of increased *NO production. These iNOS transduced cells were more susceptible to doxorubicin than vector control or wild-type cells. Cell cycle progression of iNOS transduced cells was not different from controls. Likewise, iNOS transduction resulted in no change in cellular glutathione levels. For comparison, we examined the effect of iNOS transduction on the sensitivity of MCF-7 to edelfosine, a membrane-localizing anticancer drug without direct DNA interaction. Insertion of the iNOS had no effect on killing of the MCF-7 cells by this ether lipid class drug. We also tested the effect of iNOS transduction on doxorubicin sensitivity of H9c2 rat heart-derived myoblasts. We found no augmentation of cytotoxicity by *NO, and this observation offers potential therapeutic tumor selectivity by using *NO with doxorubicin. Therefore, we conclude that *NO produced intracellularly by iNOS overexpression or delivered as a bolus sensitizes human breast cancer cells in culture to doxorubicin, but not to a cardiac cell line or to edelfosine. This augmentation is not due to a modulation of cell cycle distribution or measurable cellular glutathione resulting from the transduction.