Real-Time Evaluation of Absolute, Cytosolic, Free Ca2+ and Corresponding Contractility in Isolated, Pressurized Lymph Vessels.

The lymphatic vasculature, now often referred to as "the third circulation," is located in many vital organ systems. A principal mechanical function of the lymphatic vasculature is to return fluid from extracellular spaces back to the central venous ducts. Lymph transport is mediated by spontaneous rhythmic contractions of lymph vessels (LVs). LV contractions are largely regulated by the cyclic rise and fall of cytosolic, free calcium ([Ca2+]i). This paper presents a method to concurrently calculate changes in absolute concentrations of [Ca2+]i and vessel contractility/rhythmicity in real time in isolated, pressurized LVs. Using isolated rat mesenteric LVs, we studied changes in [Ca2+]i and contractility/rhythmicity in response to drug addition. Isolated LVs were loaded with the ratiometric Ca2+-sensing indicator Fura-2AM, and video microscopy coupled with edge-detection software was used to capture [Ca2+]i and diameter measurements continuously in real time. The Fura-2AM signal from each LV was calibrated to the minimum and maximum signal for each vessel and used to calculate absolute [Ca2+]i. Diameter measurements were used to calculate contractile parameters (amplitude, end diastolic diameter, end systolic diameter, calculated flow) and rhythmicity (frequency, contraction time, relaxation time) and correlated with absolute [Ca2+]i measurements.

Doxorubicin­induced cardiomyopathy is mitigated by empagliflozin via the modulation of endoplasmic reticulum stress pathways.

Doxorubicin (Dox) exhibits a high efficacy in the treatment of numerous types of cancer. However, the beneficial cytotoxic effects of Dox are often accompanied by an increase in the risk of cardiotoxicity. Oxidative stress (OS) plays a key role in Dox­induced cardiomyopathy (DIC). OS in cardiomyocytes disrupts endoplasmic reticulum (ER) function, leading to the accumulation of misfolded/unfolded proteins known as ER stress. ER stress acts as an adaptive mechanism; however, prolonged ER stress together with OS may lead to the initiation of cardiomyocyte apoptosis. The present study aimed to explore the potential of an anti­diabetic drug, empagliflozin (EMPA), in mitigating Dox­induced ER stress and cardiomyocyte apoptosis. In the present study, the effects of 1 h pretreatment of EMPA on Dox­treated cardiomyocytes isolated from Sprague­Dawley rats were investigated. After 24 h, EMPA pre­treatment promoted cell survival in the EMPA + Dox group compared with the Dox group. Results of the present study also demonstrated that EMPA mitigated overall ER stress, as the increased expression of ER stress markers was reduced in the EMPA + Dox group. Additionally, OS, inflammation and expression of ER stress apoptotic proteins were also significantly reduced following EMPA pre­treatment in the EMPA + Dox group. Thus, EMPA may exert beneficial effects on Dox­induced ER stress and may exhibit potential changes that can be utilised to further evaluate the role of EMPA in mitigating DIC.

Lipidomic Predictors of Coronary No-Reflow.

The 'no-reflow' phenomenon (NRP) after primary percutaneous coronary intervention (PCI) is a serious complication among acute ST-segment elevation myocardial infarction (STEMI) patients. Herein, a comprehensive lipidomics approach was used to quantify over 300 distinct molecular species in circulating plasma from 126 patients with STEMI before and after primary PCI. Our analysis showed that three lipid classes: phosphatidylcholine (PC), alkylphosphatidylcholine (PC(O)), and sphingomyelin (SM), were significantly elevated (p < 0.05) in no-reflow patients before primary PCI. The levels of individual fatty acids and total fatty acid levels were significantly lower (p < 0.05) in no-reflow subjects after PCI. The grouping of patients based on ECG ST-segment resolution (STR) also demonstrated the same trend, confirming the possible role of these differential lipids in the setting of no-reflow. Sphingomyelin species, SM 41:1 and SM 41:2, was invariably positively correlated with corrected TIMI frame count (CTFC) at pre-PCI and post-PCI. The plasma levels of SM 42:1 exhibited an inverse association (p < 0.05) consistently with tumor necrosis factor-alpha (TNF-α) at pre-PCI and post-PCI. In conclusion, we identified plasma lipid profiles that distinguish individuals at risk of no-reflow and provided novel insights into how dyslipidemia may contribute to NRP after primary PCI.

NF-κB, A Potential Therapeutic Target in Cardiovascular Diseases.

Cardiovascular diseases (CVDs) are the leading cause of death globally. Atherosclerosis is the basis of major CVDs - myocardial ischemia, heart failure, and stroke. Among numerous functional molecules, the transcription factor nuclear factor κB (NF-κB) has been linked to downstream target genes involved in atherosclerosis. The activation of the NF-κB family and its downstream target genes in response to environmental and cellular stress, hypoxia, and ischemia initiate different pathological events such as innate and adaptive immunity, and cell survival, differentiation, and proliferation. Thus, NF-κB is a potential therapeutic target in the treatment of atherosclerosis and related CVDs. Several biologics and small molecules as well as peptide/proteins have been shown to regulate NF-κB dependent signaling pathways. In this review, we will focus on the function of NF-κB in CVDs and the role of NF-κB inhibitors in the treatment of CVDs.

Olive oil protects against progression of heart failure by inhibiting remodeling of heart subsequent to myocardial infarction in rats.

We examined the beneficial effects of olive oil against heart failure post-myocardial infarction (PMI), induced by coronary artery ligation in rats. Animals were divided into sham and ligated groups and fed either regular chow, olive oil (10% wt/wt), or corn oil (10% wt/wt) and were followed up to 16 weeks. On the echocardiography at 3 days (PMI), in the ligated regular chow (LRC), ligated olive oil (LOO), and ligated corn oil (LCO) left ventricular ejection fraction (LVEF) decrease was 12.14%, 16.42%, and 17.53% from the baseline, respectively. However, only LOO group improved LVEF significantly at 16 weeks PMI and became comparable with all sham groups. Both scar formation and collagen deposition at 16 weeks PMI were less pronounced in the LOO group. Myocardial TNF-α level at 4 weeks of PMI increased by 176%, 11%, and 181% in the LRC, LOO, and LCO groups, respectively. Plasma TNF-α levels in LOO were significantly lower than LRC group after 4 weeks of PMI. Myocardial redox ratio (reduced glutathione/oxidized glutathione) decreased at 4 weeks PMI by 44.4%, 16.4%, and 36.9% in the LRC, LOO, and LCO groups, respectively, compared to the baseline. These changes in the redox ratio at 16 weeks PMI were further exacerbated in the LRC and LCO groups. Lipid hydroperoxides formation increased at 4 weeks PMI by 137.4%, 14.6%, and 97.1% in the LRC, LOO, and LCO groups, respectively. Since coronary artery ligation decreased left ventricular ejection fraction, increased myocardial TNF-α and oxidative stress, and since olive oil was able to inhibit these effects, it is proposed that dietary olive oil modulates cardiac remodeling and heart failure subsequent to myocardial infarction.

The structural basis of effective LOX-1 inhibition.

Along with other scavenger receptors, splice variants of LOX-1 play an important role in modulating numerous subcellular mechanisms such as normal cell development, differentiation and growth in response to physiological stimuli. Thus, LOX-1 activity is a key regulator in determining the severity of many genetic, metabolic, cardiovascular, renal, and neurodegenerative diseases and/or cancer. Increased expression of LOX-1 precipitates pathological disorders during the aging process. Therefore, it becomes important to develop novel LOX-1 inhibitors based on its ligand binding polarity and/or affinity and disrupt the uptake of its ligand: oxidized low-density lipoproteins (ox-LDL). In this review, we shed light on the presently studied and developed novel LOX-1 inhibitors that may have potential for treatment of diseases characterized by LOX-1 activation.

Interleukin-10 Mitigates Doxorubicin-Induced Endoplasmic Reticulum Stress as Well as Cardiomyopathy.

The use of doxorubicin (Dox) in cancer patients carries the risk of cardiotoxicity via an increase in oxidative stress, mitochondrial dysfunction, and disturbed endoplasmic reticulum (ER) homeostasis in cardiomyocytes. The present study explores which of the ER transmembrane sensors is involved in Dox-induced apoptosis and whether interleukin-10 (IL-10) has any mitigating effect. There was a time-related increase in apoptosis in cardiomyocytes exposed to 5.43 µg/mL Dox for 0 to 48 h. Dox treatment for 24 h significantly upregulated glucose-regulated proteins 78 and 94, protein disulfide isomerase, cleavage of activating transcription factor 6α, and X-box binding protein 1. These Dox-induced changes in ER stress proteins as well as apoptosis were blunted by IL-10 (10 ng/mL). In Dox-exposed cardiomyocytes, IL-10 also promoted expression of protein kinase-like endoplasmic reticulum kinase and inositol-requiring kinase 1α, which helped in maintaining ER homeostasis. Additionally, under Dox-treatment, IL-10 downregulated caspase-12 activation as well as phosphorylation of c-JUN NH2-terminal kinase, thereby promoting cardiomyocyte survival. IL-10 was able to reduce the overexpression of mitochondrial apoptotic proteins caspase-3 as well as Bax, which were upregulated upon Dox treatment. Thus, a reduction in Dox-induced ER stress as well as apoptosis through IL-10 may provide a significant benefit in improving cardiac function.

Endoplasmic Reticulum Stress Promotes iNOS/NO and Influences Inflammation in the Development of Doxorubicin-Induced Cardiomyopathy.

Doxorubicin (Dox) is known to cause heart failure in some cancer patients. Despite extensive studies over the past half century, the subcellular basis of Dox-induced cardiomyopathy (DIC) is still elusive. Earlier, we suggested that Dox causes a delayed activation of unfolded protein response (UPR) which may promote mitochondrial Bax activity leading to cardiomyocyte death. As a follow up, using NO donor, S-Nitroso-N-acetyl-d,l-penicillamine (SNAP), and/or NOS inhibitor, N(ω)-nitro-L-arginine methyl ester (L-NAME), we now show that endoplasmic reticulum (ER) stress promotes inflammation through iNOS/NO-induced TLR2 activation. In vivo Dox treatment increased mitochondrial iNOS to promote ER stress as there was an increase in Bip (Grp78) response, proapoptotic CHOP (DDIT3) and ER-mediated Caspase 12 activation. Increased iNOS activity is associated with an increase in TLR2 and TNF-α receptor associated factor 2 (TRAF2). These two together with NF-κB p105/50 expression and a synergistic support through ER stress, promote inflammatory response in the myocardium leading to cell death and ultimately fostering DIC conditions. In the presence of NOS inhibitor, such detrimental effects of Dox were inhibited, suggesting iNOS/NO as key mediators of Dox-induced inflammatory as well as apoptotic responses.

Role of oxidative stress versus lipids in monocrotaline-induced pulmonary hypertension and right heart failure.

Pulmonary hypertension (PH) is a global health issue with a prevalence of 10% in ages >65 years. Right heart failure (RHF) is the main cause of death in PH. We have previously shown that monocrotaline (MCT)-induced PH and RHF are due to an increase in oxidative stress. In this study, probucol (PROB), a strong antioxidant with a lipid-lowering property, versus lovastatin (LOV), a strong lipid-lowering drug with some antioxidant effects, were evaluated for their effects on the MCT-induced RHF. Rats were treated (I.P.) with PROB (10 mg/kg ×12) or LOV (4 mg/kg ×12), daily 6 days before and 6 days after a single MCT injection (60 mg/kg). Serial echocardiography was performed and at 4-week post-MCT, lung wet-to-dry weight, hemodynamics, RV glutathione peroxidase (GSHPx), superoxide dismutase (SOD), catalase, lipid peroxidation, and myocardial as well as plasma lipids were examined. MCT increased RV systolic and diastolic pressures, wall thickness, RV end diastolic diameter, mortality, and decreased ejection fraction as well as pulmonary artery acceleration time. These changes were mitigated by PROB while LOV had no effect. Furthermore, PROB prevented lipid peroxidation, lowered lipids, and increased GSHPx and SOD in RV myocardium. LOV did decrease the lipids but had no effect on antioxidants and lipid peroxidation. A reduction in oxidative stress and not the lipid-lowering effect of PROB may explain the prevention of MCT-induced PH, RHF, and mortality. Thus targeting of oxidative stress as an adjuvant therapy is suggested.

Study of ER stress and apoptotic proteins in the heart and tumor exposed to doxorubicin.

Although a high cumulative dose of Doxorubicin (Dox) is known to cause cardiotoxicity, there is still a lack of understanding of the subcellular basis of this drug-induced cardiomyopathy. Differential effects of Dox on mitochondria and endoplasmic reticulum (ER) were examined in cardiomyocytes, tumor cells, implanted tumors and hearts of normal as well as tumor-bearing animals. Dox increased mitochondrial (Mito) Bax activation at 3 h in the cardiomyocyte without change in the DNA damage inducible transcriptor-3 (DDIT3) expression in the ER. Increased DDIT3 in these Dox-treated cardiomyocytes at 24 h suggested that increased MitoBax may have promoted ER stress related changes in DDIT3. Dissociation of immunoglobulin-binding protein (Bip) from activating transcription factor 6 (ATF6)-Bip complex in the ER was observed as an adaptive response to Dox. In contrast, breast cancer MCF7 cells showed an ER stress response to Dox with increased DDIT3 as early as 3 h which may have triggered a positive feedback activation of ATF6 at 12 and 24 h and promoted Calnexin. At these later time points, increased Bax activation in cancer cells suggested that MitoBax may be controlled by DDIT3 or by Calnexin. DDIT3 response in tumors was evoked by Dox, however this response was inversely correlated with increased Bip and Bax expression in hearts from tumor bearing animals. It is suggested that in Dox-induced cardiotoxicity both mitochondrial and ER stresses play an integral role through a mutual interaction where an inhibition of DDIT3 or Calnexin may also be crucial to achieve Dox resistance in cardiomyocytes.

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.

IL-10 attenuates OxPCs-mediated lipid metabolic responses in ischemia reperfusion injury.

Oxidized phospholipids (OxPLs) promote inflammation as well as low density lipoprotein (LDL) uptake in a variety of physiological and pathological states. Given the anti-inflammatory role of the cytokine IL-10, we investigated its modulatory effect on the production of oxidized phosphatidylcholines (OxPCs) as well as lipid metabolic responses in global myocardial ischemia/reperfusion (I/R) injury. Increased OxPCs levels, by 1-Palmitoyl-2-(5-oxovaleryl)-sn-glycero-3-phosphocholine (POVPC), promoted oxidative stress (OS) and cell death. OxPCs-mediated-OS, resulted in oxidized low-density lipoprotein receptor 1 (LOX-1) activation and upregulated the expression of toll-like receptor 2 (TLR2). IL-10-induced increase in proprotein convertase subtilisin/kexin type 9 (PCSK9) negatively regulated LOX-1 as well as TLR2 inflammatory responses. Under stress conditions, phosphorylation of sterol regulatory element binding protein 1c (SREBP 1c) was prevented by IL-10. The latter also prevented the generation of OxPCs and reduced their ratio (OxPCs/PCs) during injury. LOX-1 activation also promoted SREBP1c-mediated TGF-ßRII expression which was inhibited by IL-10. Both fragmented and non-fragmented OxPCs were elevated during I/R and this effect was attenuated by IL-10. The largest impact (two-threefold change at log2) was on PAzPC, (1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine)-a fragmented OxPC. Thus it appears that among different OxPCs, IL-10 significantly reduces a single molecule (PAzPC)-mediated lipid metabolic responses in cardiomyocytes thereby mitigating inflammation and cell death.

Blueberry extract attenuates doxorubicin-induced damage in H9c2 cardiac cells 1.

The objective of this study was to analyze the cardioprotective roles of 3 wild blueberry genotypes and one commercial blueberry genotype by measuring markers of oxidative stress and cell death in H9c2 cardiac cells exposed to doxorubicin. Ripe berries of the 3 wild blueberry genotypes were collected from a 10-year-old clearcut forest near Nipigon, Ontario, Canada (49°1'39″N, 87°52'21″W), whereas the commercial blueberries were purchased from a local grocery store. H9c2 cardiac cells were incubated with 15 µg gallic acid equivalent/mL blueberry extract for 4 h followed by 5 µM doxorubicin for 4 h, and oxidative stress and active caspase 3/7 were analyzed. The surface area as well as total phenolic content was significantly higher in all 3 wild blueberry genotypes compared with the commercial species. Increase in oxidative stress due to doxorubicin exposure was attenuated by pre-treatment with all 3 types of wild blueberries but not by commercial berries. Furthermore, increase in caspase 3/7 activity was also attenuated by all 3 wild genotypes as well. These data demonstrate that wild blueberry extracts can attenuate doxorubicin-induced damage to H9c2 cardiomyocytes through reduction in oxidative stress and apoptosis, whereas the commercial blueberry had little effect.

Molecular hydrogen: potential in mitigating oxidative-stress-induced radiation injury 1.

Uncontrolled production of oxygen and nitrogen radicals results in oxidative and nitrosative stresses that impair cellular functions and have been regarded as causative common denominators of many pathological processes. In this review, we report on the beneficial effects of molecular hydrogen in scavenging radicals in an artificial system of •OH formation. As a proof of principle, we also demonstrate that in rat hearts in vivo, administration of molecular hydrogen led to a significant increase in superoxide dismutase as well as pAKT, a cell survival signaling molecule. Irradiation of the rats caused a significant increase in lipid peroxidation, which was mitigated by pre-treatment of the animals with molecular hydrogen. The nuclear factor erythroid 2-related factor 2 is regarded as an important regulator of oxyradical homeostasis, as well as it supports the functional integrity of cells, particularly under conditions of oxidative stress. We suggest that the beneficial effects of molecular hydrogen may be through the activation of nuclear factor erythroid 2-related factor 2 pathway that promotes innate antioxidants and reduction of apoptosis, as well as inflammation.

Innate immune response in the pathogenesis of heart failure in survivors of myocardial infarction.

Among the different cardiovascular disease complications, atherosclerosis-induced myocardial infarction (MI) is the major contributor of heart failure (HF) and loss of life. This review presents short- and long-term features of post-MI in human hearts and animal models. It is known that the heart does not regenerate, and thus loss of cardiac cells after an MI event is permanent. In survivors of a heart attack, multiple neurohumoral adjustments as well as simultaneous remodeling in both infarcted and noninfarcted regions of the heart help sustain pump function post-MI. In the early phase, migration of inflammatory cells to the infarcted area helps repair and remove the cell debris, while apoptosis results in the elimination of damaged cardiomyocytes, and there is an increase in the antioxidant response to protect the survived myocardium against oxidative stress (OS) injury. However, in the late phase, it appears that there is a relative increase in OS and activation of the innate inflammatory response in cardiomyocytes without any obvious inflammatory cells. In this late stage in survivors of MI, a progressive slow activation of these processes leads to apoptosis, fibrosis, cardiac dysfunction, and HF. Thus, this second phase of an increase in OS, innate inflammatory response, and apoptosis results in wall thinning, dilatation, and consequently HF. It is important to note that this inflammatory response appears to be innate to cardiomyocytes. Blunting of this innate immune cardiomyocyte response may offer new hope for the management of HF.

Vitamin C mitigates oxidative/nitrosative stress and inflammation in doxorubicin-induced cardiomyopathy.

Increase in oxidative/nitrosative stress is one of the mechanisms associated with the development of cardiotoxicity due to doxorubicin (Dox), a potent chemotherapy drug. Previously, we reported mitigation of Dox-induced oxidative/nitrosative stress and apoptosis by vitamin C (Vit C) in isolated cardiomyocytes. In the present in vivo study in rats, we investigated the effect of prophylactic treatment with Vit C on Dox-induced apoptosis, inflammation, oxidative/nitrosative stress, cardiac dysfunction, and Vit C transporter proteins. Dox (cumulative dose: 15 mg/kg) in rats reduced systolic and diastolic cardiac function and caused structural damage. These changes were associated with a myocardial increase in reactive oxygen species, reduction in antioxidant enzyme activities, increased expression of apoptotic proteins, and inflammation. Dox also caused an increase in the expression of proapoptotic proteins Bax, Bnip-3, Bak, and caspase-3. An increase in oxidative/nitrosative stress attributable to Dox was indicated by an increase in superoxide, protein carbonyl formation, lipid peroxidation, nitric oxide (NO), NO synthase (NOS) activity, protein nitrosylation, and inducible NOS protein expression. Dox increased the levels of cardiac proinflammatory cytokines TNF-α, IL-1ß, and IL-6, whereas the expression of Vit C transporter proteins (sodium-ascorbate cotransporter 2 and glucose transporter 4) was reduced. Prophylactic and concurrent treatment with Vit C prevented all these changes and improved survival in the Vit C + Dox group. Vit C also improved Dox-mediated systolic and diastolic dysfunctions and structural damage. These results suggest a cardioprotective role of Vit C in Dox-induced cardiomyopathy by reducing oxidative/nitrosative stress, inflammation, and apoptosis, as well as improving Vit C transporter proteins.NEW & NOTEWORTHY This in vivo study provides novel data that vitamin C improves cardiac structure and function in doxorubicin-induced cardiomyopathy by reducing oxidative/nitrosative stress, apoptosis, and inflammation along with upregulation of cardiac vitamin C transporter proteins. The latter may have a crucial role in improving antioxidant status in this cardiomyopathy.

Toll-like receptor 2 dominance over Toll-like receptor 4 in stressful conditions for its detrimental role in the heart.

It has been suggested that Toll-like receptor (TLR)4 promotes IL-10-mediated cardiac cell survival, whereas another receptor, TLR2, from the same family, is detrimental. Here, we examined the interactive role of these two innate signaling molecules under stressful conditions, including IL-10 knockout (IL-10-/-) mice, global ischemia-reperfusion (I/R) injury in rat hearts, and in vitro short hairpin RNA experimental models in the presence or absence of IL-10 (10 ng/ml). Circulating and myocardial levels of TNF-α as well as apoptosis and fibrosis were higher in IL-10-/- mice. The increase in TLR2 in IL-10-/- hearts indicated its negative regulation by IL-10. Ex vivo I/R also caused a marked upregulation of TLR2 and TNF-α as well as apoptotic and fibrotic signals. However, a 40-min reperfusion with IL-10 triggered an increase in TLR4 expression and improved recovery of cardiac function. The increase in IL-1 receptor-associated kinase (IRAK)-M and IRAK-2 activity during I/R injury suggested their role in TLR2 signaling. In vitro inhibition of TLR4 activity as a consequence of RNA inhibition-mediated suppression of myeloid differentiation gene (MyD)88 suggested MyD88-dependent activation of TLR4. The inclusion of IL-10 during reperfusion also downregulated the expression of IRAK-2, TNF-α receptor-associated factor 1-interacting protein (TRAIP) and apoptotic signals, caspase-3, and the Bax-to-Bcl-xL ratio. IL-10 reduced the TNF-α receptor-associated increase in TRAIP-induced apoptosis during I/R injury, which led to an increase in IL-1ß to mitigate transforming growth factor-ß receptor type I-mediated fibrosis. The IL-10 mitigation of these changes suggests that the stimulation through TLR4 signaling promotes IRAK-4 and phosphorylates IRAK-1 instead of IRAK-2 and may be an important therapeutic approach in restoring heart health in stress.NEW & NOTEWORTHY Under stress conditions such as downregulation of the IL-10 gene or ischemia-reperfusion injury, Toll-like receptor (TLR)4 and IL-1 receptor-associated kinase (IRAK)-1 activation is suppressed, along with the upregulation of TLR-2 and IRAK-2, resulting in fibrosis and apoptosis. It is suggested that IL-10 helps to maintain heart function during stress via myeloid differentiation gene 88/IRAK-4/IRAK-1-dependent TLR4 signaling.

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases.

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)-induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1) control, 2) Vit C (25 µM), 3) Dox (10 µM), and 4) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O2·-), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O2·-, which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity.

Insulin resistance: an additional risk factor in the pathogenesis of cardiovascular disease in type 2 diabetes.

Sedentary life style and high calorie dietary habits are prominent leading cause of metabolic syndrome in modern world. Obesity plays a central role in occurrence of various diseases like hyperinsulinemia, hyperglycemia and hyperlipidemia, which lead to insulin resistance and metabolic derangements like cardiovascular diseases (CVDs) mediated by oxidative stress. The mortality rate due to CVDs is on the rise in developing countries. Insulin resistance (IR) leads to micro or macro angiopathy, peripheral arterial dysfunction, hampered blood flow, hypertension, as well as the cardiomyocyte and the endothelial cell dysfunctions, thus increasing risk factors for coronary artery blockage, stroke and heart failure suggesting that there is a strong association between IR and CVDs. The plausible linkages between these two pathophysiological conditions are altered levels of insulin signaling proteins such as IR-ß, IRS-1, PI3K, Akt, Glut4 and PGC-1α that hamper insulin-mediated glucose uptake as well as other functions of insulin in the cardiomyocytes and the endothelial cells of the heart. Reduced AMPK, PFK-2 and elevated levels of NADP(H)-dependent oxidases produced by activated M1 macrophages of the adipose tissue and elevated levels of circulating angiotensin are also cause of CVD in diabetes mellitus condition. Insulin sensitizers, angiotensin blockers, superoxide scavengers are used as therapeutics in the amelioration of CVD. It evidently becomes important to unravel the mechanisms of the association between IR and CVDs in order to formulate novel efficient drugs to treat patients suffering from insulin resistance-mediated cardiovascular diseases. The possible associations between insulin resistance and cardiovascular diseases are reviewed here.