Antioxidant effect of acetyl-l-carnitine against cisplatin-induced cardiotoxicity

Objective

Cisplatin (CDDP) toxicity is a dose-limiting clinical problem in clinical practice, mainly because of nephrotoxicity or ototoxicity. However, the mechanism of CDDP-induced cardiotoxicity is poorly understood. Acetyl-l-carnitine (ALCAR) is an antioxidant agent with protective effects against the side effects of various chemotherapeutics. CDDP-induced cardiotoxicity and the protective role of ALCAR were evaluated in this study.

Methods

Morphological changes were evaluated in hematoxylin and eosin-stained sections, and immunohistochemistry for caspase-3, superoxide dismutase-2 (SOD-2), inducible nitrite oxide synthase (iNOS), cyclooxygenase-2, and Bcl-2 was performed using the hearts of athymic nude mice carrying xenograft neuroblastoma tumors. Mice were randomized (six/group) to the control, CDDP (16 mg/kg), and ALCAR (200 mg/kg)+CDDP (16 mg/kg) groups. Results were analyzed using nonparametric tests.

Results

No difference was observed in the rates of cardiac necrosis, dilated/congested blood vessels, hemorrhage, polymorphonuclear leukocyte infiltration, edema, and pyknotic nuclei among the groups. SOD-2 expression was increased in the CDDP group but not in the ALCAR+CDDP group. iNOS, Bcl-2, and caspase-3 levels were not significantly different among the groups.

Conclusions

ALCAR might be a candidate protective agent for CDDP-induced cardiotoxicity. SOD-2, as a member of the oxidant system, should be evaluated in further studies as a biomarker of cardiotoxicity.

Dynamic Phosphorylation of the C Terminus of Hsp70 Regulates the Mitochondrial Import of SOD2 and Redox Balance

The import of superoxide dismutase-2 (SOD2) into mitochondria is vital for the survival of eukaryotic cells. SOD2 is encoded within the nuclear genome and translocated into mitochondria for activation after translation in the cytosol. The molecular chaperone Hsp70 modulates SOD2 activity by promoting import of SOD2 into mitochondria. In turn, the activity of Hsp70 is controlled by co-chaperones, particularly CHIP, which directs Hsp70-bound proteins for degradation in the proteasomes. We investigated the mechanisms controlling the activity of SOD2 to signal activation and maintain mitochondrial redox balance. We demonstrate that Akt1 binds to and phosphorylates the C terminus of Hsp70 on Serine631, which inhibits CHIP-mediated SOD2 degradation thereby stabilizing and promoting SOD2 import. Conversely, increased mitochondrial-H₂O₂ formation disrupts Akt1-mediated phosphorylation of Hsp70, and non-phosphorylatable Hsp70 mutants decrease SOD2 import, resulting in mitochondrial oxidative stress. Our findings identify Hsp70 phosphorylation as a physiological mechanism essential for regulation of mitochondrial redox balance.

Oxidative stress pathways in pancreatic β-cells and insulin-sensitive cells and tissues: importance to cell metabolism, function, and dysfunction

It is now accepted that nutrient abundance in the blood, especially glucose, leads to the generation of reactive oxygen species (ROS), ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensatory response from antioxidant mechanisms, the cell, or indeed the tissue, becomes overwhelmed by oxidative stress, leading to the activation of intracellular stress-associated pathways. Activation of the same or similar pathways also appears to play a role in mediating insulin resistance, impaired insulin secretion, and late diabetic complications. The ability of antioxidants to protect against the oxidative stress induced by hyperglycemia and elevated free fatty acid (FFA) levels in vitro suggests a causative role of oxidative stress in mediating the latter clinical conditions. In this review, we describe common biochemical processes associated with oxidative stress driven by hyperglycemia and/or elevated FFA and the resulting clinical outcomes: β-cell dysfunction and peripheral tissue insulin resistance.

Strong SOD2 expression and HPV-16/18 positivity are independent events in cervical cancer

It is well known that persistent infection with high-risk HPV (hr-HPV), mostly HPV-16 and 18, is the main cause of cervical cancer development. Manganese superoxide dismutase (MnSOD or SOD2) are highly expressed in different neoplasia. The present study investigated SOD2 protein expression and the presence of hr-HPV types in 297 cervical samples including non-neoplastic tissue, cervical intraepithelial neoplasia grade 3 (CIN3), squamous cell carcinoma (SCC) and adenocarcinoma (ADC). Strong SOD2 expression was significantly higher in ADC (82%) than CIN3 (52%) or SCC (64%). There was no association between SOD2 expression and HPV 16 and/or 18 detection for every lesion analyzed. Binary Logist Regression revealed that strong SOD2 expression (OR: 27.50, 6.16-122.81) and HPV 16 and/or HPV 18 (OR: 12.67, 4.04-39.74) were independently more associated with CIN3 than non-neoplastic cervix. Strong SOD2 expression (OR: 3.30, 1.23-8.86) and HPV 16 and/or HPV 18 (OR: 3.51, 1.03-11.87) were independently more associated with ADC than SCC. Similar findings for SOD2 expression were observed by the Cochran Mantel-Haenszel test, controlling for HPV-16 and/or HPV 18. In conclusion, the expression of SOD2 was increased in CIN3 and SCC, and more increased in cervical ADC than in SCC. Strong SOD2 expression was statistically independent of the presence of HPV 16 and/or 18. These findings suggest that the mitochondrial antioxidant system and HPV infection could follow independent pathways in the carcinogenesis of cervical epithelium and in the differentiation to SCC or ADC of the cervix.

Resistin and visfatin in steatotic and non-steatotic livers in the setting of partial hepatectomy under ischemia-reperfusion

BACKGROUND & AIMS

This study examined whether the regulation of resistin and visfatin could reduce damage and improve regeneration in both steatotic and non-steatotic livers undergoing partial hepatectomy under ischemia-reperfusion, a procedure commonly applied in clinical practice to reduce bleeding.

METHODS

Resistin and visfatin were pharmacologically modulated in lean and obese animals undergoing partial hepatectomy under ischemia-reperfusion.

RESULTS

No evident role for these adipocytokines was observed in non-steatotic livers. However, obese animals undergoing liver surgery showed increased resistin in liver and plasma, without changes in adipose tissue, together with visfatin downregulation in liver and increment in plasma and adipose tissue. Endogenous resistin maintains low levels of visfatin in the liver by blocking its hepatic uptake from the circulation, thus regulating the visfatin detrimental effects on hepatic damage and regenerative failure. Indeed, the administration of anti-resistin antibodies increased hepatic accumulation of adipocyte-derived visfatin, exacerbating damage and regenerative failure. Interestingly, treatment with anti-visfatin antibodies protected steatotic livers, and similar results were obtained with the concomitant inhibition of resistin and visfatin. Thus, when visfatin was inhibited, the injurious effects of anti-resistin antibodies disappeared. Herein we show that upregulation of visfatin increased NAD levels in the remnant steatotic liver, whereas visfatin inhibition decreased them. These later observations suggest that visfatin may favour synthesis of NAD instead of DNA and induces alterations in amino acid metabolism-urea cycle and NO production, overall negatively affecting liver viability.

CONCLUSIONS

Our results indicate the clinical potential of visfatin blocking-based therapies in steatotic livers undergoing partial hepatectomy with ischemia-reperfusion.

(-)-Epicatechin rich cocoa mediated modulation of oxidative stress regulators in skeletal muscle of heart failure and type 2 diabetes patients

BACKGROUND

Type 2 diabetes (T2D) and heart failure (HF) are associated with high levels of skeletal muscle (SkM) oxidative stress (OS). Health benefits attributed to flavonoids have been ascribed to antioxidation. However, for flavonoids with similar antioxidant potential, end-biological effects vary widely suggesting other mechanistic venues for reducing OS. Decreases in OS may follow the modulation of key regulatory pathways including antioxidant levels (e.g. glutathione) and enzymes such as mitochondrial superoxide dismutase (SOD2) and catalase.

METHODS

We examined OS-related alterations in SkM in T2D/HF patients (as compared vs. healthy controls) and evaluated the effects of three-month treatment with (-)-epicatechin (Epi) rich cocoa (ERC). To evidence Epi as the mediator of the improved OS profile we examined the effects of pure Epi (vs. water) on SkM OS regulatory systems in a mouse model of insulin resistance and contrasted results vs. normal mice.

RESULTS

There were severe alterations in OS regulatory systems in T2D/HF SkM as compared with healthy controls. Treatment with ERC induced recovery in glutathione levels and decreases in the nitrotyrosilation and carbonylation of proteins. With treatment, key transcriptional factors translocate into the nucleus leading to increases in SOD2 and catalase protein expression and activity levels. In insulin resistant mice, there were alterations in muscle OS and pure Epi replicated the beneficial effects of ERC found in humans.

CONCLUSIONS

Major perturbations in SkM OS can be reversed with ERC in T2D/HF patients. Epi likely mediates such effects and may provide an effective means to treat conditions associated with tissue OS.

Uncoupling protein-2 regulates lifespan in mice

The long-term effects of uncoupled mitochondrial respiration by uncoupling protein-2 (UCP2) in mammalian physiology remain controversial. Here we show that increased mitochondrial uncoupling activity of different tissues predicts longer lifespan of rats compared with mice. UCP2 reduces reactive oxygen species (ROS) production and oxidative stress throughout the aging process in different tissues in mice. The absence of UCP2 shortens lifespan in wild-type mice, and the level of UCP2 positively correlates with the postnatal survival of superoxide dismutase-2 mutant animals. Thus UCP2 has a beneficial influence on cell and tissue function leading to increased lifespan.