Epigenetic modifier alpha-ketoglutarate modulates aberrant gene body methylation and hydroxymethylation marks in diabetic heart

BACKGROUND

Diabetic cardiomyopathy (DCM) is a leading cause of death in diabetic patients. Hyperglycemic myocardial microenvironment significantly alters chromatin architecture and the transcriptome, resulting in aberrant activation of signaling pathways in a diabetic heart. Epigenetic marks play vital roles in transcriptional reprogramming during the development of DCM. The current study is aimed to profile genome-wide DNA (hydroxy)methylation patterns in the hearts of control and streptozotocin (STZ)-induced diabetic rats and decipher the effect of modulation of DNA methylation by alpha-ketoglutarate (AKG), a TET enzyme cofactor, on the progression of DCM.

METHODS

Diabetes was induced in male adult Wistar rats with an intraperitoneal injection of STZ. Diabetic and vehicle control animals were randomly divided into groups with/without AKG treatment. Cardiac function was monitored by performing cardiac catheterization. Global methylation (5mC) and hydroxymethylation (5hmC) patterns were mapped in the Left ventricular tissue of control and diabetic rats with the help of an enrichment-based (h)MEDIP-sequencing technique by using antibodies specific for 5mC and 5hmC. Sequencing data were validated by performing (h)MEDIP-qPCR analysis at the gene-specific level, and gene expression was analyzed by qPCR. The mRNA and protein expression of enzymes involved in the DNA methylation and demethylation cycle were analyzed by qPCR and western blotting. Global 5mC and 5hmC levels were also assessed in high glucose-treated DNMT3B knockdown H9c2 cells.

RESULTS

We found the increased expression of DNMT3B, MBD2, and MeCP2 with a concomitant accumulation of 5mC and 5hmC, specifically in gene body regions of diabetic rat hearts compared to the control. Calcium signaling was the most significantly affected pathway by cytosine modifications in the diabetic heart. Additionally, hypermethylated gene body regions were associated with Rap1, apelin, and phosphatidyl inositol signaling, while metabolic pathways were most affected by hyperhydroxymethylation. AKG supplementation in diabetic rats reversed aberrant methylation patterns and restored cardiac function. Hyperglycemia also increased 5mC and 5hmC levels in H9c2 cells, which was normalized by DNMT3B knockdown or AKG supplementation.

CONCLUSION

This study demonstrates that reverting hyperglycemic damage to cardiac tissue might be possible by erasing adverse epigenetic signatures by supplementing epigenetic modulators such as AKG along with an existing antidiabetic treatment regimen.

Regulation of peroxiredoxin-3 gene expression under basal and hyperglycemic conditions: Key roles for transcription factors Sp1, CREB and NF-κB

Peroxiredoxin-3 (Prx-3), a thioredoxin-dependent peroxidase located exclusively in the mitochondrial matrix, catalyses peroxides/peroxinitrites. Altered levels of Prx-3 is associated with diabetic cardiomyopathy (DCM). However, molecular mechanisms of Prx-3 gene regulation remain partially understood. We undertook a systemic analysis of the Prx-3 gene to identify the key motifs and transcriptional regulatory molecules. Transfection of promoter-reporter constructs in the cultured cells identified -191/+20 bp domain as the core promoter region. Stringent in silico analysis of this core promoter revealed putative binding sites for specificity protein 1 (Sp1), cAMP response element-binding protein (CREB) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Interestingly, while co-transfection of the -191/+20 bp construct with Sp1/CREB plasmid diminished Prx3 promoter-reporter activity, mRNA and protein levels, co-transfection with NF-κB expression plasmid augmented the same. Consistently, inhibition of Sp1/CREB/NF-κB expression reversed the promoter-reporter activity, mRNA and protein levels of Prx-3, thereby confirming their regulatory effects. ChIP assays provided evidence for interactions of Sp1/CREB/NF-κB with the Prx-3 promoter. H9c2 cells treated with high glucose as well as streptozotocin (STZ)-treated diabetic rats showed time-dependent reduction in promoter activity, endogenous transcript and protein levels of Prx-3. Augmentation of Sp1/CREB protein levels and their strong binding with Prx-3 promoter are responsible for diminished Prx-3 levels under hyperglycemia. The activation/increase in the NF-κB expression under hyperglycemia was not sufficient to restore the reduction of endogenous Prx-3 levels owing to its weak binding affinity. Taken together, this study elucidates the previously unknown roles of Sp1/CREB/NF-κB in regulating Prx-3 gene expression under hyperglycemic condition.

Mitochondrial Peroxiredoxin-3 protects against hyperglycemia induced myocardial damage in Diabetic cardiomyopathy

Mitochondrial oxidative stress has emerged as a key contributor towards the development of diabetic cardiomyopathy. Peroxiredoxin-3 (Prx-3), a mitochondrial antioxidant, scavenges H2O2 and offers protection against ROS related pathologies. We observed a decrease in the expression of Prx-3 in the hearts of streptozotocin (STZ) induced diabetic rats, and also high glucose treated H9c2 cardiac cells, which may augment oxidative stress mediated damage. Hence we hypothesized that overexpression of Prx-3 could prevent the cardiac damage associated with diabetes. In this study we used quercetin (QUE) to achieve Prx-3 induction in vivo, while a Prx-3 overexpressing H9c2 cell line was employed for carrying out in vitro studies. Diabetes was induced in Wistar rats by a single intraperitoneal injection of STZ. Quercetin (50mg/kg body weight) was delivered orally to hyperglycemic and age matched control rats for 2 months. Quercetin treatment induced the myocardial expression of Prx-3 but not Prx-5 both in control and STZ rats. Prx-3 induction by quercetin prevented diabetes induced oxidative stress as confirmed by decrease in expression of markers such as 4-HNE and mitochondrial uncoupling protein, UCP-3. It was also successful in reducing cardiac cell apoptosis, hypertrophy and fibrosis leading to amelioration of cardiac contractility defects. Overexpression of Prx-3 in cultured H9c2 cardiac cells could significantly diminish high glucose inflicted mitochondrial oxidative damage and apoptosis, thus strengthening our hypothesis. These results suggest that diabetes induced cardiomyopathy can be prevented by elevating Prx-3 levels thereby providing extensive protection to the diabetic heart.

A novel SOD mimic with a redox-modulating mn (II) complex, ML1 attenuates high glucose-induced abnormalities in intracellular Ca2+ transients and prevents cardiac cell death through restoration of mitochondrial function

A key contributor to the pathophysiology of diabetic cardiomyopathy, mitochondrial superoxide can be adequately countered by Mn-superoxide dismutase, which constitutes the first line of defense against mitochondrial oxidative stress. Our group has recently synthesized low molecular weight SOD mimics, demonstrating superior protection against oxidative damages to kidney cells. In the current study, we sought to evaluate the protective effect of the SOD mimic ML1 against high glucose induced cardiomyopathy in diabetes. Mechanistic studies using rat cardiac myoblast H9c2 showed that ML1 markedly inhibited High Glucose (HG) induced cytotoxicity. This was associated with increased Mn-SOD expression along with decreased mitochondrial [Formula: see text], ONOO- and Ca²⁺ accumulation, unveiling its anti-oxidant potentials. ML1 also attenuated HG-induced loss of mitochondrial membrane potential (ΔΨ_m) and release of cytochrome c, suggesting that ML1 effectuates its cytoprotective action via the preservation of mitochondrial function. In an ex-vivo model normal adult rat ventricular myocytes (ARVMs) were isolated and cultured in either normal glucose (5.5 mmol/l glucose) or HG (25.5 mmol/l glucose) conditions and the efficiency of ML-1 was analyzed by studying contractile function and calcium indices. Mechanical properties were assessed using a high-speed video-edge detection system, and intracellular Ca²⁺ transients were recorded in fura-2-loaded myocytes. Pretreatment of myocytes with ML1 (10 nM) ameliorated HG induced abnormalities in relaxation including depressed peak shortening, prolonged time to 90% relenghthening, and slower Ca²⁺ transient decay. Thus, ML1 exhibits significant cardio protection against oxidative damage, perhaps through its potent antioxidant action via activation of Mn-SOD.

Monoamine oxidase-A is an important source of oxidative stress and promotes cardiac dysfunction, apoptosis, and fibrosis in diabetic cardiomyopathy

Oxidative stress is closely associated with the pathophysiology of diabetic cardiomyopathy (DCM). The mitochondrial flavoenzyme monoamine oxidase A (MAO-A) is an important source of oxidative stress in the myocardium. We sought to determine whether MAO-A plays a major role in modulating DCM. Diabetes was induced in Wistar rats by single intraperitoneal injection of streptozotocin (STZ). To investigate the role of MAO-A in the development of pathophysiological features of DCM, hyperglycemic and age-matched control rats were treated with or without the MAO-A-specific inhibitor clorgyline (CLG) at 1 mg/kg/day for 8 weeks. Diabetes upregulated MAO-A activity; elevated markers of oxidative stress such as cardiac lipid peroxidation, superoxide dismutase activity, and UCP3 protein expression; enhanced apoptotic cell death; and increased fibrosis. All these parameters were significantly attenuated by CLG treatment. In addition, treatment with CLG substantially prevented diabetes-induced cardiac contractile dysfunction as evidenced by decreased QRS, QT, and corrected QT intervals, measured by ECG, and LV systolic and LV end-diastolic pressure measured by microtip pressure transducer. These beneficial effects of CLG were seen despite the persistent hyperglycemic and hyperlipidemic environments in STZ-induced experimental diabetes. In summary, this study provides strong evidence that MAO-A is an important source of oxidative stress in the heart and that MAO-A-derived reactive oxygen species contribute to DCM.

Multiple antioxidants improve cardiac complications and inhibit cardiac cell death in streptozotocin-induced diabetic rats

Diabetic cardiomyopathy, a disorder of the heart muscle in diabetic patients, is one of the major causes of heart failure. Since diabetic cardiomyopathy is now known to have a high prevalence in the asymptomatic diabetic patient, prevention at the earliest stage of development by existing molecules would be appropriate in order to prevent the progression of heart failure. In this study, we investigated the protective role of multiple antioxidants (MA), on cardiac dysfunction and cardiac cell apoptosis in streptozotocin (STZ)-induced diabetic rat. Diabetic cardiomyopathy in STZ-treated animals was characterized by declined systolic, diastolic myocardial performance, oxidative stress and apoptosis in cardiac cells. Diabetic rats on supplementation with MA showed decreased oxidative stress evaluated by the content of reduced levels of lipid per-oxidation and decreased activity of catalase with down-regulation of heme-oxygenase-1 mRNA. Supplementation with MA also resulted in a normalized lipid profile and decreased levels of pro-inflammatory transcription factor NF-kappaB as well as cytokines such as TNF-α, IFN-γ, TGF-β, and IL-10. MA was found to decrease the expression of ROS-generating enzymes like xanthine oxidase, monoamine oxidase-A along with 5-Lipoxygenase mRNA and/or protein expression. Further, left ventricular function, measured by a microtip pressure transducer, was re-established as evidenced by increase in ±dp/dtmax, heart rate, decreased blood pressure, systolic and diastolic pressure as well as decrease in the TUNEL positive cardiac cells with increased Bcl-2/Bax ratio. In addition, MA supplementation decreased cell death and activation of NF-kappaB in cardiac H9c2 cells. Based on our results, we conclude that MA supplementation significantly attenuated cardiac dysfunction in diabetic rats; hence MA supplementation may have important clinical implications in terms of prevention and management of diabetic cardiomyopathy.

High glucose-induced Ca2+ overload and oxidative stress contribute to apoptosis of cardiac cells through mitochondrial dependent and independent pathways

BACKGROUND

Cardiac cell apoptosis is the initiating factor of cardiac complications especially diabetic cardiomyopathy. Mitochondria are susceptible to the damaging effects of elevated glucose condition. Calcium overload and oxidative insult are the two mutually non-exclusive phenomena suggested to cause cardiac dysfunction. Here, we examined the effect of high-glucose induced calcium overload in calpain-1 mediated cardiac apoptosis in an in vitro setting.

METHODS

H9c2, rat ventricular myoblast cell line was treated with elevated glucose condition and the cellular consequences were studied. Intracellular calcium trafficking, ROS generation, calpain-1 activation and caspase-12 and caspase-9 pathway were studied using flow cytometry, confocal microscopy and Western blot analysis.

RESULTS

High-glucose treatment resulted in increased intracellular calcium ([Ca2+]i) which was mobilized to the mitochondria. Concomitant intra-mitochondrial calcium ([Ca2+]m) increase resulted in enhanced reactive oxygen and nitrogen species generation. These events led to mitochondrial dysfunction and apoptosis. Cardiomyocyte death exhibited several classical markers of apoptosis, including activation of caspases, appearance of annexin V on the outer plasma membrane, increased population of cells with sub-G0/G1 DNA content and nuclear condensation. Key findings include elucidation of cell signaling mechanism of high-glucose induced calcium-dependent cysteine protease calpain-1 activation, which triggers non-conventional caspases as alternate mode of cell death.

CONCLUSION

This information increases the understanding of cardiac cell death under hyperglycemic condition and can possibly be extended for designing new therapeutic strategies for diabetic cardiomyopathy.

GENERAL SIGNIFICANCE

The novel findings of the study reveal that high glucose induces apoptosis by both mitochondria-dependent and independent pathways via concomitant rise in intracellular calcium.

Azelnidipine prevents cardiac dysfunction in streptozotocin-diabetic rats by reducing intracellular calcium accumulation, oxidative stress and apoptosis

BACKGROUND

Numerous evidences suggest that diabetic heart is characterized by compromised ventricular contraction and prolonged relaxation attributable to multiple causative factors including calcium accumulation, oxidative stress and apoptosis. Therapeutic interventions to prevent calcium accumulation and oxidative stress could be therefore helpful in improving the cardiac function under diabetic condition.

METHODS

This study was designed to examine the effect of long-acting calcium channel blocker (CCB), Azelnidipine (AZL) on contractile dysfunction, intracellular calcium (Ca2+) cycling proteins, stress-activated signaling molecules and apoptosis on cardiomyocytes in diabetes. Adult male Wistar rats were made diabetic by a single intraperitoneal (IP) injection of streptozotocin (STZ). Contractile functions were traced from live diabetic rats to isolated individual cardiomyocytes including peak shortening (PS), time-to-PS (TPS), time-to-relengthening (TR90), maximal velocity of shortening/relengthening (± dL/dt) and intracellular Ca2+ fluorescence.

RESULTS

Diabetic heart showed significantly depressed PS, ± dL/dt, prolonged TPS, TR90 and intracellular Ca2+ clearing and showed an elevated resting intracellular Ca2+. AZL itself exhibited little effect on myocyte mechanics but it significantly alleviated STZ-induced myocyte contractile dysfunction. Diabetes increased the levels of superoxide, enhanced expression of the cardiac damage markers like troponin I, p67phox NADPH oxidase subunit, restored the levels of the mitochondrial superoxide dismutase (Mn-SOD), calcium regulatory proteins RyR2 and SERCA2a, and suppressed the levels of the anti-apoptotic Bcl-2 protein. All of these STZ-induced alterations were reconciled by AZL treatment.

CONCLUSION

Collectively, the data suggest beneficial effect of AZL in diabetic cardiomyopathy via altering intracellular Ca2+ handling proteins and preventing apoptosis by its antioxidant property.

Azelnidipine protects myocardium in hyperglycemia-induced cardiac damage

Background

Azelnidipine (AZL), a long-acting dihydropyridine-based calcium antagonist, has been recently approved and used for treating ischemic heart disease and cardiac remodeling after myocardial infarction, however, its effect on hyperglycemia-induced cardiac damage has not been studied.

Methods

This study examined the effect of AZL on circulating markers of cardiac damage, altered lipid and cytokines profile and markers of oxidative stress including homocysteine in diabetic rats.

Results

STZ induced diabetes caused a significant increase in blood glucose levels. It also resulted in an increase in the levels of homocysteine and cardiac damage markers, like Troponin-1, CK-MB, CK-NAC, uric acid, LDH and alkaline phosphatase. Moreover, there was an increase in the levels of proinflammatory cytokines like TNF-α, IFN-γ, and TGF-β and decrease in the levels of IL-4 and IL-10. Additionally, there was increase in the levels of cholesterol, triglycerides, LDL, VLDL and a decrease in HDL in these animals. There was an altered antioxidant enzyme profile which resulted in a notable increase in the levels of oxidative stress markers like lipid peroxides, nitric oxide and carbonylated proteins. Compared with the untreated diabetic rats, AZL treatment significantly reduced the levels of troponin-1 (P < 0.05), CK-MB (P < 0.05), CK-NAC (P < 0.05), uric acid (P < 0.05), LDH (P < 0.05) and alkaline phosphatase (P < 0.05). It also reduced the levels of the TNF-α (P < 0.05), IFN-γ (P < 0.05), and TGF-β (P < 0.05) and increased the levels of IL-4 (P < 0.05). A significant decrease in the serum cholesterol (P < 0.05), triglycerides (P < 0.05), LDL (P < 0.05), VLDL (P < 0.05) and a significant rise in levels of HDL (P < 0.05) was also observed. Treatment with AZL corrected the distorted antioxidant enzyme profile resulting in a significant decrease in the levels of lipid peroxides, nitric oxide and carbonylated proteins.

Conclusion

Our results indicate that AZL treatment can reduce the risk of hyperglycemia induced metabolic disorders and its role can be further extended to explore its therapeutic potential in diabetic patients with cardiac complications.

Cardiotoxicity of calmidazolium chloride is attributed to calcium aggravation, oxidative and nitrosative stress, and apoptosis

The intracellular calcium concentration ([Ca](i)) regulates cell viability and contractility in myocardial cells. Elevation of the [Ca](i) level occurs by entry of calcium ions (Ca(2+)) through voltage-dependent Ca(2+) channels in the plasma membrane and release of Ca(2+) from the sarcoplasmic reticulum. Calmidazolium chloride (CMZ), a subgroup II calmodulin antagonist, blocks L-type calcium channels as well as voltage-dependent Na(+) and K(+) channel currents. This study elaborates on the events that contribute to the cytotoxic effects of CMZ on the heart. We hypothesized that apoptotic cell death occurs in the cardiac cells through calcium accumulation, production of reactive oxygen species, and the cytochrome c-mediated PARP activation pathway. CMZ significantly increased the production of superoxide (O(2)(*-)) and nitric oxide (NO) as detected by FACS and confocal microscopy. CMZ induced mitochondrial damage by increasing the levels of intracellular calcium, lowering the mitochondrial membrane potential, and thereby inducing cytochrome c release. Apoptotic cell death was observed in H9c2 cells exposed to 25 microM CMZ for 24 h. This is the first report that elaborates on the mechanism of CMZ-induced cardiotoxicity. CMZ causes apoptosis by decreasing mitochondrial activity and contractility indices and increasing oxidative and nitrosative stress, ultimately leading to cell death via an intrinsic apoptotic pathway.

N-acetylcysteine prevents glucose/glucose oxidase-induced oxidative stress, mitochondrial damage and apoptosis in H9c2 cells

AIMS

High blood glucose may auto-oxidize and generate free radicals, which are proposed to induce apoptosis in cardiac cells. The aim of the present study was to investigate the cell damage induced by glucose/glucose oxidase-dependent oxidative stress and the protective effect of N-acetylcysteine (NAC) on H9c2 cardiac muscle cells.

MAIN METHODS

H9c2 cells were exposed to 33 mM glucose (G)+1.6 milliunits (mU) of glucose oxidase (GO) and termed G/GO. Cell apoptosis, generation of reactive oxygen species (ROS-super oxide anion and hydrogen peroxide) and reactive nitrogen species (RNS-peroxinitrite), and the change in mitochondrial membrane potential (DeltaPsim) was studied using flow cytometry and confocal microscopy, and cytochrome c release was measured using confocal microscopy. The expression of Bcl-2, Bax and the activation of procaspase-9 was studied by western blot.

KEY FINDINGS

Exposure of H9c2 cells to G/GO resulted in a significant increase in cellular apoptosis (P<0.05) and the generation of ROS and RNS (P<0.001). Further, G/GO treatment led to a decrease in DeltaPsim, release of cytochrome c, decrease in Bcl-2, increase in Bax expression and the activation of procaspase-9. Treatment with NAC significantly decreased apoptosis (P<0.05) and reduced the levels of ROS and RNS (P<0.001). NAC was also able to normalize DeltaPsim, inhibit cytochrome c release, increase Bcl-2 and decrease Bax expression and procaspase-9 activation.

SIGNIFICANCE

Our studies suggest that NAC has antioxidative and antiapoptotic activity against G/GO-induced oxidative stress through the inhibition of mitochondrial damage in H9c2 cells.

Cytoprotective and antioxidant role of diallyl tetrasulfide on cadmium induced renal injury: An in vivo and in vitro study

Cadmium (Cd) is an environmental and industrial pollutant that affects various organs in humans and animals. A body of evidence has accumulated implicating the free radical generation with subsequent oxidative stress in the biochemical and molecular mechanisms of Cd toxicity. Since kidney is the critical target of Cd toxicity, we carried out this study to investigate the effects of diallyl tetrasulfide (DTS), an organosulfur compound derived from garlic on Cd induced toxicity in the kidney of rats and also in the kidney cell line (vero cells). In experimental rats, subcutaneous administration of Cd (3 mg/kg bw/day) for 3 weeks induced renal damage, which was evident from significantly increased levels of serum urea and creatinine with significant decrease in creatinine clearance. A markedly increased levels of lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) and protein carbonyl contents with significant decrease in nonenzymic antioxidants (total sulphydryl groups, reduced glutathione, vitamin C and vitamin E) and enzymic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase) as well as glutathione metabolizing enzymes (glutathione reductase, and glucose-6-phosphate dehydrogenase) were also observed in Cd intoxicated rats. Coadministration of DTS (40 mg/kg bw/day) and Cd resulted in the reversal of the kidney function accompanied by a significant decrease in lipid peroxidation and increase in the antioxidant defense system. In vitro studies with vero cells showed that incubation of DTS (5-50 microg/ml) with Cd (10 microM) significantly reduced the cell death induced by Cd. DTS at 40 microg/ml effectively blocked the cell death and lipid peroxidation induced by Cd (10 microM) indicating its cytoprotective property. Further, the flow cytometric assessment on the level of intracellular reactive oxygen species using a fluorescent probe 2', 7'-dichlorofluorescein diacetate (DCF-DA) confirmed the Cd induced intracellular oxidative stress in vero cells, which was significantly suppressed by DTS (40 microg/ml). The histopathological studies in the kidney of rats also showed that DTS (40 mg/kg bw/day) markedly reduced the toxicity of Cd and preserved the architecture of renal tissue. The present study suggests that the cytoprotective potential of DTS in Cd toxicity might be due to its antioxidant and metal chelating properties, which could be useful for achieving optimum effects in Cd induced renal damage.

Cadmium induced mitochondrial injury and apoptosis in vero cells: Protective effect of diallyl tetrasufide from garlic

Oxidative stress and mitochondrial injury has been implicated in cadmium-induced apoptosis. In this study, we examined the protective effect of diallyl tetrasulfide from garlic on cadmium induced oxidative stress and apoptosis in vero cells. Exposure of vero cells to cadmium (10 microM) for 18 h showed the apoptotic events such as loss of cell viability, alterations in nuclear morphology and decreased mitochondrial membrane potential with significantly increased levels of reactive oxygen species (super oxide anion and hydrogen peroxide). Treatment of vero cells with cadmium (10 microM) and diallyl tetrasulfide (5-50 microg/ml) showed that diallyl tetrasulfide attenuated the cadmium-induced suppression of cell viability in a dose dependent manner and highly significant effect was observed at 40 microg/ml. The nuclei morphological analysis with 4',6-diamidino-2-phenylindole staining confirmed that diallyl tetrasulfide at 40 microg/ml prevented the Cd (10 microM) induced apoptosis. Flow cytometric analysis with 2',7'-dichlorofluorencein diacetate showed that the inhibitory effect of diallyl tetrasulfide (10-40 microg/ml) on reactive oxygen species generation parallel with its effect on cell viability. In addition, diallyl tetrasulfide (40 microg/ml) remarkably reduced the cadmium-induced accumulation of superoxide radical and hydrogen peroxide with in cells. Further, diallyl tetrasulfide significantly protected the cadmium-induced decrease in mitochondrial membrane potential, an indicator of mitochondrial function. Our study suggest that diallyl tetrasulfide affect the reactive oxygen species generation induced by cadmium, and possesses a novel protective effect on the cytolethality associated with mitochondrial injury, which contributes to the antiapoptotic effect of diallyl tetrasulfide against cadmium.

Role of bittergourd fruit juice in stz-induced diabetic state in vivo and in vitro

The aqueous juice of bittergourd fruit (BF) (Momordica charantia L.) of the family Cucurbitaceae has been shown to possess hypoglycemic activity. However, the mechanism of its action is not known. Hence in vitro and in vivo experiments were carried out to study the role of BF juice on the diabetic status. The activity of BF juice was tested on STZ treated RIN cells and isolated islets in vitro. It was found that feeding with BF juice caused reduction in STZ-induced hyperglycemia in mice. It markedly reduced the STZ-induced lipid peroxidation in pancreas of mice, RIN cells and islets. Further it also reduced the STZ-induced apoptosis in RIN cells indicating the mode of protection of BF juice on RIN cells, islets and pancreatic beta-cells. Present study thus confirms hypoglycemic effect of BF juice and provides sufficient documentation to define its role and action for its potential and promising use in treating diabetes.

Effect of cryopreservation on lipid peroxidation in chick cornea

A mechanism suggested to cause injury to the preserved organs in vitro is the generation of oxygen free radicals either during preservation or after transplantation due to reperfusion. Methods to suppress generation of oxygen free radicals may lead to improved methods of organ preservation. In this study, increase in the levels of lipid peroxidation in chick cornea after cryopreservation is reported. Addition of fetal bovine serum (FBS) in cryopreservation medium was found to prevent lipid peroxidation. Addition of FBS was also found to be protective towards corneal viability during cryopreservation.

Divalent cations and radiation induced lipid peroxidation

Response of Co2+, Cu2+, Fe2+, Ni2+ and Mn2+ against radiation induced lipid peroxidation has been examined. Liposomes prepared from L-alpha-lecithin were irradiated with or without divalent cations, Co2+ and Cu2+ inhibited lipid peroxidation in concentration dependent manner. On the other hand Fe2+, Ni2+ and Mn2+ enhanced the peroxidation. The enhancement of peroxidation due to Ni2+ was biphasic in nature. Higher concentration of Mn2+ decreased the peroxidation. Except Cu2+ no other cation studied could change the non-linear pattern of radiation induced lipid peroxidation. The pro- or antioxidant effect of divalent cations may be due to their reactivity towards oxygen and oxygen free radicals, and at least in part to their hard/soft acid character.

Non-linear pattern of radiation induced lipid peroxidation is not affected by vitamin E, Fe2+ ions and molecular oxygen

Results of the present study on liposomes have clearly shown that non-linear pattern of radiation-induced lipid peroxidation was not changed even in the presence of vitamin E, Fe2+ ions or molecular oxygen. These results are important from biological point of view as lipid peroxidation is used as a measure of membrane damage.

Modification of radiation induced lipid peroxidation by calmodulin antagonists

It has been shown that calmodulin antagonists provide radio-protection in euoxic and sensitization in hypoxic conditions. This differential protection in euoxic conditions might have arisen from the interaction of calmodulin antagonists with oxygen free radicals. This possibility has been tested in the present communication. Radiation induced lipid peroxidation process in liposomes has been used for this purpose. Liposomes prepared from L-alpha-lecithin were irradiated with or without calmodulin antagonists. Calmodulin antagonists inhibited lipid peroxidation significantly. The inhibition was found to increase with increase in concentration of the drugs. These observations suggest that calmodulin antagonists have a capacity to scavenge oxygen free radicals involved in initiation and/or propagation of lipid peroxidation process. This may be the reason for their differential radioprotection in euoxic conditions in biological systems.