Vanillic acid mitigates hyperinsulinemia induced ER stress mediated altered calcium homeostasis, MAMs distortion and surplus lipogenesis in HepG2 cells

Hyperinsulinemia (HI) induced insulin resistance (IR) and associated pathologies are the burning and unsolvable issues in diabetes treatment. The cellular, molecular and biochemical events associated with HI are not yet elucidated. Similarly, no focused research on designing therapeutic strategies with natural products for attenuation of HI are seen in literature. Keeping this in mind we planned the present study to evaluate the alterations occurring at ER/Ca²⁺ homeostasis/mitochondria associated endoplasmic reticulum membranes (MAMs) in HepG2 cells during HI and to evaluate the possible beneficial effect of vanillic acid (VA) to mitigate the complications. An in vitro model of HI was established by treating HepG2 cells with human insulin (1 μM) for 24 h. Then, ER stress, Ca²⁺ homeostasis, MAMs, IR and hepatic lipogenesis were studied at protein level. Various proteins critical to ER, Ca²⁺ homeostasis and MAMs such as p-IRE-1α, ATF6, p-PERK, p-eIF2α, CHOP, XBP1, p-CAMKII, InsP3R, SERCA, JNK, GRP78, VDAC, Cyp D, GRP75, MFN2, PTEN and mTORC were studied and found altered significantly causing ER stress, defect in Ca²⁺ movements and distortion of MAMs. The decreased expression of IRS2 and an unaltered expression of IRS1 confirmed the development of selective insulin resistance in hepatocytes during HI and this was the crucial factor for the progression of the hepatic lipid accumulation. We found simultaneous treatment of VA is beneficial up to a certain extent to protect HepG2 cells from the adverse effect of HI via its antioxidant, antilipogenic, mitochondrial and ER protection properties.

Tangeretin alleviates Tunicamycin-induced endoplasmic reticulum stress and associated complications in skeletal muscle cells

Endoplasmic reticulum (ER) stress and associated oxidative stress are involved in the genesis and progression of skeletal muscle diseases such as myositis and atrophy or muscle wasting. Targeting the ER stress and associated downstream pathways can aid in the development of better treatment strategies for these diseases with limited therapeutic approaches. There is a growing interest in identifying natural products against ER stress due to the lower toxicity and cost effectiveness. In the present study, we investigated the protective effect of Tangeretin, a citrus methoxyflavone found in citrus peels against Tunicamycin (pharmacological ER stress inducer)-induced ER stress and associated complications in rat skeletal muscle L6 cell lines. Treatment with Tunicamycin for a period of 24 h resulted in the upregulation of ER stress marker proteins, ER resident oxidoreductases and cellular reactive oxygen species (ROS). Co-treatment with Tangeretin was effective in alleviating Tunicamycin-induced ER stress and associated redox-related complications by significantly downregulating the unfolded protein response (UPR), ER resident oxidoreductase proteins, cellular ROS and improving the antioxidant enzyme activity. Tunicamycin also induced upregulation of phosphorylated p38 MAP Kinase and loss of mitochondrial membrane potential. Tangeretin significantly reduced the levels of phosphorylated p38 MAP Kinase and improved the mitochondrial membrane potential. From the results, it is evident that Tangeretin can be explored further as a potential candidate for skeletal muscle diseases involving protein misfolding and ER stress.

In vitro and in vivo anti-inflammatory and anti-arthritic effect of Tinospora cordifolia via modulation of JAK/STAT pathway

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory disorder causing cartilage and joint degeneration. In spite of the availability of several robust drugs like biologics, most of the patients are unresponsive, and reports of severe adverse effects following long-term use are also there. Subsequently the use of natural plant-based products in RA therapy is broadening over the years. Tinospora cordifolia is a widely used medicinal plant in Ayurveda against various inflammatory disorders including RA. However, there is very limited knowledge regarding the actual molecular events responsible for its therapeutic effect, and this has limited its acceptance among the professionals.

PURPOSE

To explore the anti-inflammatory and anti-arthritic effect of hydro-alcoholic extract from Tinospora cordifolia.

METHODS

The rich polyphenol nature of the extract was elucidated using HPLC. LPS-stimulated murine macrophage cell line RAW 264.7 was used for in vitro studies, and collagen-induced arthritis (CIA) model was used for in vivo studies.

RESULTS

The polyphenols in TCE were identified using HPLC. TCE effectively downregulated the level of pro-inflammatory mediators (IL-6, TNF-α, PGE2, and NO) in LPS-stimulated RAW 264.7 cells. Subsequently the upregulated expression of COX-2 and iNOS following LPS stimulation were also downregulated by TCE. Furthermore, TCE targeted the upstream kinases of the JAK/STAT pathway, a crucial inflammatory pathway. The expression of VEGF, a key angiogenic factor as well as an inflammatory mediator was also decreased following pre-treatment with TCE. The anti-arthritic effect of TCE (150 mg/kg) was evaluated in the CIA model as well. From the results of histopathology, oral administration of TCE was found to be effective in reducing the clinical symptoms of arthritis including paw edema, erythema, and hyperplasia. In vivo results validated the in vitro results and there was a significant reduction in serum level of pro-inflammatory cytokines and mediators (IL-6, TNF-α, IL-17, NO, and PGE2). The phosphorylation of STAT3 and the expression of VEGF were also downregulated following TCE treatment.

CONCLUSION

Our study provided a detailed insight into the molecular events associated with anti-inflammatory and anti-arthritic effect of Tinospora cordifolia.

Ferulic acid attenuates high glucose-induced MAM alterations via PACS2/IP3R2/FUNDC1/VDAC1 pathway activating proapoptotic proteins and ameliorates cardiomyopathy in diabetic rats

BACKGROUND

Diabetic cardiomyopathy (DCM) is one of the severe complications of diabetes with no known biomarkers for early detection. Mitochondria-associated endoplasmic reticulum membranes (MAM) are less studied subcellular targets but an emerging area for exploration in metabolic disorders including DCM. We herein studied the role of MAMs and downstream mitochondrial functions in DCM. We also explored the efficacy of ferulic acid (FeA) against DCM via modulation of MAM and its associated signaling pathway.

METHODS

The H9c2 cardiomyoblast cells were incubated with high concentration (33 mM) of d-glucose for 48 h to create a high glucose ambience in vitro. The expression of various critical proteins of MAM, mitochondrial function, oxidative phosphorylation (OxPhos) and the genesis of apoptosis were examined. The rats fed with high fat/high fructose/streptozotocin (single dose, i.p.) were used as a diabetic model and analyzed the insulin resistance and markers of cardiac hypertrophy and apoptosis.

RESULTS

High glucose conditions caused the upregulation of MAM formation via PACS2, IP3R2, FUNDC1, and VDAC1 and decreased mitochondrial biogenesis, fusion and OxPhos. The upregulation of mitochondria-driven SMAC-HTRA2-ARTS-XIAP apoptosis and other cell death pathways indicate their critical roles in the genesis of DCM at the molecular level. The diabetic rats also showed cardiomyopathy with increased heart mass index, TNNI3K, troponin, etc. FeA effectively prevented the high glucose-induced MAM alterations and associated cellular anomalies both in vitro and in vivo.

CONCLUSION

High glucose-induced MAM distortion and subsequent mitochondrial dysfunctions act as the stem of cardiomyopathy. MAM could be explored as a potential target to treat diabetic cardiomyopathy. Also, the FeA could be an attractive nutraceutical agent for diabetic cardiomyopathy.

Cinnamic acid is beneficial to diabetic cardiomyopathy via its cardioprotective, anti-inflammatory, anti-dyslipidemia, and antidiabetic properties

Diabetes-related health issues are increasing day by day in public, and diabetic cardiomyopathy (DCM) is one serious issue among them. There is a lack of proper strategy to control and manage DCM. Here we are attempting a nutraceutical-based approach to protect the heart from DCM. The beneficial effect of cinnamic acid (CiA), was evaluated in an experimental model of diabetes. For this, diabetic model was created by feeding male Wistar rats with a high fat, high fructose diet for 6 months and a single dose of streptozotocin (25 mg/kg bwt). Metformin was used as the positive control. The diabetic rats showed insulin resistance, myocardial injury, and a significant increase of total cholesterol, triglycerides, and LDL. Development of DCM was evident from the increased cardiac mass index, LDH, CKMB, ANP, and CRP levels in the diabetic group. There was a significant increase in the levels of cardiac hypertrophy markers like TGF-β and β-MHC in the hearts of diabetic rats revealing DCM. Pro-inflammatory cytokines (TNF-α, IL-6) and lipid peroxides were significantly elevated in the serum of diabetic rats. Histopathology revealed inflammation and necrosis in the heart of diabetic rats confirming DCM. Oral administration of CiA (5 and 10 mg/kg bwt) prevented the development of DCM via its cardioprotective, anti-inflammatory, anti-dyslipidemia potential, and antidiabetic properties. Similarly, metformin (50 mg/kg bwt) has also shown protection against DCM. We conclude from this study that CiA is found to be beneficial against DCM and recommend more detailed preclinical and clinical studies to develop CiA-based nutraceutical against DCM.

A novel aureothin diepoxide derivative from Streptomyces sp. NIIST-D31 strain

A novel vicinal diepoxide of alloaureothin was isolated from Streptomyces sp. NIIST-D31 strain along with three carboxamides, p-aminobenzoic acid and 1,6-dimethoxyphenazine. Exhaustive 2D NMR analysis and analysis of experimental, theoretical CD spectra aided in establishing the structure of compound 1. Compound 1 inhibits adipogenesis and accumulation of lipid droplets during the differentiation of 3T3-L1 cells.

Pretreatment of hydroethanolic extract of Dillenia indica L. attenuates oleic acid induced NAFLD in HepG2 cells via modulating SIRT-1/p-LKB-1/AMPK, HMGCR & PPAR-α signaling pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Dillenia indica L. is an edible plant from the Dilleniaceae family present in the forest of India and other Asian countries. Different parts of this plant are being used in the traditional system of medicines for various diseases like diabetes, indigestion, asthma, jaundice, and rheumatic pain by various rural communities. This plant is very common among Khamptis traditional healers, the rural community of the Dhemaji district of Assam, ethnic communities of Dibru-Saikhowa Biosphere Reserve of Northeast, India for various medicinal uses. It is observed as a 'vat' suppressant and 'pitta' boosting medicine in Ayurveda.

AIM OF THE STUDY

The aim of this research was to evaluate the effect of hydroethanolic extract of Dillenia indica leaf (DI-HET) against non-alcoholic fatty liver disease (NAFLD) as it is reported effective against jaundice in traditional medicine. We are also planning to see the various molecular mechanisms responsible for its effect if it is efficacious.

STUDY DESIGN/METHOD

An in vitro model for NAFLD was employed in this study. For this HepG2 cells were incubated with 100 μM of oleic acid (OA) for 24 h. For evaluation of the effect of DI-HET, the extracts (5 or 10 μg/mL) were pretreated to the OA group. Fenofibrate was the positive control. Various parameters relevant to lipogenesis and β-oxidation of fatty acids like intracellular lipid accumulation, reactive oxygen species (ROS), mitochondrial stress, and key proteins were studied.

RESULTS

DI-HET significantly reduced the intracellular lipid accumulation in OA treated cells. And also substantially decreased the expression of lipogenic proteins and increased β-oxidation in the OA group. OA induced ROS generation was found to reduce with DI-HET treatment. Western blot analysis showed that the expression of LXR-α, SREBP-1C, SREBP-2, HMGCR, FAS, CD-36, and ACOX-1 were downregulated while that of SIRT-1, p-LKB-, p-AMPK, p-ACC, CPT-1, and PPAR-α upregulated in DI-HET treatment. LCMS/MS analysis showed the presence of polyphenols like naringenin, catechin, epicatechin, shikimic acid, syringic acid, vanillic acid, and kaempferol.

CONCLUSION

These results suggest that DI-HET is effective against NAFLD by activation of the SIRT-1/p-LKB-1/AMPK signaling pathway via polyphenols present in the extract.

Methylglyoxal induces ambience for cancer promotion in HepG2 cells via Warburg effect and promotes glycation

Methylglyoxal (MGO) is a toxic, highly reactive metabolite derived mainly from glucose and amino acids degradation. MGO is also one of the prime precursors for advanced glycation end products formation. The present research was performed to check whether MGO has any role in the promotion of cancer in HepG2 cells. For this, cells were incubated with MGO (50 µM) for 24 h and subjected to various analyses. Aminoguanidine (200 µM) was positive control. The various biochemical and protein expression studies, relevant to the MGO detoxification system, oxidative stress, and glycolysis were performed. MGO caused the reduction of expression of GLO 1 (27%) and GLO 2 (11%) causing weakening of the innate detoxification system. This is followed by an increase of RAGE (95%), AGEs or methylglyoxal adducts. We also observed hypoxia via estimation of oxygen consumption rate and surplus reactive oxygen species (ROS) (24%). To investigate the off-target effect of MGO we checked its effect on glucose transport, and its associated proteins. Glucose uptake was found to increase (15%) significantly with overexpression of GLUT 1 (35%). We also found a significant increase of glycolytic enzymes such as hexokinase II, phosphofructokinase 1, and lactate dehydrogenase along with lactate production. Observation of surplus ROS and enhanced glycolysis led us to check the expression of HIF 1α which is their downstream signaling pathway. Interestingly HIF 1α was found to increase significantly (35%). It is known that enhanced glycolysis and oxidative stress are catalysts for the overexpression of HIF 1α which in turn creates an ambience for the promotion of cancer. Aminoguanidine was able to prevent the adverse effect of MGO partially. This is the first study to show the potential of MGO for the promotion of cancer in the non-tumorigenic HepG2 cells via the Warburg effect and glycation.

In vitro and in vivo studies reveal the beneficial effects of chlorogenic acid against ER stress mediated ER-phagy and associated apoptosis in the heart of diabetic rat

Endoplasmic reticulum (ER) and associated signaling pathways are involved in diabetic cardiomyopathy (DCM) however, detailed studies are not available. The present study investigated the role of ER stress and related pathways such as ER-phagy, apoptosis and their underlying mechanisms using appropriate models. Beneficial effect of chlorogenic acid was also evaluated against ER stress mediated DCM. H9c2 cells with high glucose (33 mM, in vitro model of hyperglycemia) showed significant activation of ER stress response (GRP78, PERK, IRE1α, ATF6α) and altered its regulatory proteins (PDI, ERO1α). Also, it enhanced ER-phagy through upregulation of Sec62, RTN3 and downregulation of FAM134B. High glucose caused apoptosis via increased levels of CHOP, caspase 12 and calnexin. All these proteins (PERK, IRE1α, ATF6α, RTN3, Sec62 and FAM134B) have been found to have a significant role in the functioning of heart such as excitation contraction coupling and we expect these alterations to induce cardiomyopathy during diabetes. This was confirmed in in vivo study too. High fat, high fructose diet with mild streptozotocin induced diabetic rats showed an increased expression of BNP confirming cardiac injury. We also noticed severe ER stress in the heart of diabetic animals. All these have contributed significantly into alterations in histopathology and increase of weight of the hearts. These findings clearly show that ER stress plays a vital protagonist in the progression of DCM. We also found chlorogenic acid is effective against hyperglycemia induced pathological alteration both in vitro as well as in vivo.

Downregulation of TLR4/MyD88/p38MAPK and JAK/STAT pathway in RAW 264.7 cells by Alpinia galanga reveals its beneficial effects in inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Alpinia galanga, commonly known as greater galangal or raasna, is widely used in Ayurveda against various inflammatory disorders. It is also known as Kulinjan, Aratha, Rasna or Sugandhamula. Some of the Ayurvedic preparations using the rhizome of Alpinia galanga are Rasnadi kashayam, Rasna panchakam, Rasnapthakam, and Rasnarendadi. The aromatic rhizome is the source of the drug greater galangal and it is also used as a spice in South and South East Asia. However, the molecular mechanism of action of A galanga against inflammation remains poorly understood.

AIM OF THE STUDY

To elucidate the anti-inflammatory effect of hydroalcoholic extract of Alpinia galanga rhizome.

STUDY DESIGN/METHOD

The mechanism of the anti-inflammatory effect of hydroalcoholic extract of Alpinia galanga (AGE) was investigated by enzyme-linked immunosorbent assay (ELISA), Western blot, and immunofluorescence in LPS stimulated murine macrophage cell line (RAW 264.7). HPLC analysis was done to elucidate the rich polyphenolic nature of AGE.

RESULTS

The study showed that pre-treatment with AGE downregulated the release of pro-inflammatory mediators (IL-6, TNF-α, NO, and ROS) and stimulated the release of anti-inflammatory mediator IL-10 in LPS stimulated RAW 264.7 cells. The vital enzymes of inflammation (iNOS, COX-2, and MMP-9) were also downregulated by pre-treatment with AGE. AGE targeted the upstream elements of the inflammatory cascade by blocking LPS induced activation of TLR4 and JAK/STAT pathway. The phosphorylation of downstream kinases was significantly affected. The inhibition of nuclear translocation of NFκB further confirmed the specific inhibition of the TLR4 pathway. Particularly AGE inhibited the phosphorylation of JNK, p38, IκBα, and STAT. HPLC analysis of the AGE showed the polyphenol-rich nature of the extract.

CONCLUSIONS

The results from this study provide firm evidence that AGE exerts its anti-inflammatory effect via modulation of TLR4 and JAK/STAT pathway.

Zerumin A attenuates the inflammatory responses in LPS-stimulated H9c2 cardiomyoblasts

Zerumin A (ZA) is one of the potential components of Curcuma amada rhizomes, and it has been shown to possess a variety of pharmacological activities. This study deals with the beneficial activity of ZA in lipopolysaccharide (LPS)-stimulated inflammation in H9c2 cardiomyoblasts. Herein, H9c2 cells were preincubated with ZA for 1 h and stimulated with LPS for 24 h. The cells were analyzed for the expression of various pro-inflammatory mediators and signaling molecules. Results showed that the cell viability was significantly improved and reactive oxygen species production was alleviated remarkably with ZA pretreatment. We also found that ZA pretreatment significantly suppressed the upregulation of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) protein levels, and nitric oxide (NO) release in LPS-stimulated cells. In addition, ZA significantly ameliorated LPS-elicited overexpression of pro-inflammatory chemokines and cytokines such as monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor α (TNF- α), interferon-γ (IFN-γ), and interleukin-1 (IL-1) in H9c2 cells, and it upregulated the synthesis of the anti-inflammatory cytokine interleukin-10 (IL-10). Moreover, pretreatment with ZA and the mitogen-activated protein kinases (MAPK) pathway inhibitors also reduced the phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinases (JNK), and p38. ZA significantly inhibited IkB-a phosphorylation and nuclear factor (NF)-kB p65 subunit translocation into nuclei. Overall data demonstrated that ZA protects cardiomyocytes against LPS injury by inhibiting NF-kB p65 activation via the MAPK signaling pathway in vitro. These findings suggest that ZA may be a promising agent for a detailed study for the prevention or treatment of myocardial dysfunction in sepsis.

Advanced glycation end products and their adverse effects: The role of autophagy

The critical roles played by advanced glycation endproducts (AGEs) accumulation in diabetes and diabetic complications have gained intense recognition. AGEs interfere with the normal functioning of almost every organ with multiple actions like apoptosis, inflammation, protein dysfunction, mitochondrial dysfunction, and oxidative stress. However, the development of a potential treatment strategy is yet to be established. Autophagy is an evolutionarily conserved cellular process that maintains cellular homeostasis with the degradation and recycling systems. AGEs can activate autophagy signaling, which could be targeted as a therapeutic strategy against AGEs induced problems. In this review, we have provided an overview of the adverse effects of AGEs, and we put forth the notion that autophagy could be a promising targetable strategy against AGEs.

Current and novel therapeutic targets in the treatment of rheumatoid arthritis

Rheumatoid arthritis (RA), a multifactorial disease characterized by synovitis, cartilage destruction, bone erosion, and periarticular decalcification, finally results in impairment of joint function. Both genetic and environmental factors are risk factors in the development of RA. Unwanted side effects accompany most of the current treatment strategies, and around 20-40% of patients with RA do not clinically benefit from these treatments. The unmet need for new treatment options for RA has prompted research in the development of novel agents acting through physiologically and pharmacologically relevant targets. Here we discuss in detail three critical pathways, Janus kinase/signal transducer and activator of transcription (JAK/STAT), Th17, and hypoxia-inducible factor (HIF), and their roles as unique therapeutic targets in the field of RA. Some of the less developed but potential targets like nucleotide-binding and oligomerization domain-like receptor containing protein 3 (NLRP3) inflammasome and histone deacetylase 1 (HDAC1) are also discussed.

Fructose-palmitate based high calorie induce steatosis in HepG2 cells via mitochondrial dysfunction: An in vitro approach

A proper in vitro model for conducting research on high energy food induced steatosis via defective energy metabolism in the liver is not visible in the literature. The present study developed an in vitro model in HepG2 cell line to mimic high energy diet induced steatosis in liver via mitochondrial dysfunction. For this, HepG2 cells were treated with fructose (100 mM) and palmitate (100 μM) for about 24 h and subjected for biochemical analysis relevant to lipogenesis and mitochondrial biology. Our findings showed that fructose-palmitate treatment caused significant lipid accumulation and rise in lipogenic proteins. Further studies showed alteration in mitochondrial integrity, dynamics and oxidative phosphorylation. Mitochondrial integrity was affected by the dissipation of trans-membrane potential, surplus mitochondrial superoxide with calcium overload. Similarly, mitochondrial dynamics were altered with up regulation of mitochondrial fission proteins: DRP1 and FIS1, cytochrome c release, caspase-3 activity and apoptosis. Various components of the electron transport chain: complex I, II, III and IV were altered with significant depletion in oxygen consumption. Overall our findings illustrate the dominant role of mitochondria in the genesis of high fructose-palmitate induced steatosis in HepG2 cells. Since continuous high energy food consumption is the main inducer of steatosis, this model is found to be an ideal one for preliminary and basic research in the area of liver disease via mitochondrial dysfunction.

Pretreatment of Tribulus terrestris L. causes anti-ischemic cardioprotection through MAPK mediated anti-apoptotic pathway in rat

The aim of the present investigation is the evaluation and elucidation of the mechanisms by which Tribulus terrestris L. methanol extract (TTM) devoid of fruit exhibits protection against cardiac ischemia in in vitro (H9c2 cell line) and in vivo (Wistar rat) model. Tribulus terrestris L. (TT) was used in this study to evaluate the efficacy against cardiac ischemia employing in vitro and in vivo models of myocardial ischemia. H9c2 cells were used for the in vitro induction of ischemia. Male Wistar rats (10 weeks old) weighing 180-220 g were used for the in vivo experiments. ECG and clinically relevant cardiac biomarkers like serum lactate dehydrogenase, serum creatinine kinase, serum creatinine kinase myocardial B fraction, serum glutamic oxaloacetic transaminase and serum glutamic pyruvic transaminase were analysed to evaluate efficacy in the rat. For elucidation of molecular mechanisms of its beneficial activity in vitro, expression of apoptotic markers like Bax, Bad, Bcl-2 and signalling pathways involving mitogen-activated protein kinases like p38α, JNK, and Akt were studied. Tribulus terrestris L. was found effective against cardiac ischemia in the rat which was evident from ECG and various cardiac biomarkers analysis. Tribulus terrestris L. was found to act through the mitogen-activated signalling pathway leading to prevention of apoptosis during ischemic insult. The beneficial effect of Tribulus terrestris L. against cardiac ischemia was seen both in in vitro and in vivo models via its anti-apoptotic potential.

Glucotoxicity results in apoptosis in H9c2 cells via alteration in redox homeostasis linked mitochondrial dynamics and polyol pathway and possible reversal with cinnamic acid

Several mechanisms have been proposed for the heart dysfunction during hyperglycemia. The aim of the present in vitro study is to elucidate the role of alterations in redox homeostasis in the induction of apoptosis during hyperglycemia in H9c2 cells via dysfunction in mitochondria and polyol pathway and evaluation of the beneficial effect of cinnamic acid against the same. The H9c2 cells were incubated with 33 mM glucose for 48 h to simulate the diabetic condition. Cell injury was confirmed with a significant increase of atrial natriuretic peptide and lactate dehydrogenase release. Alterations in the innate antioxidant system, polyol pathway, mitochondrial integrity, dynamics and apoptosis were investigated. Hyperglycemic insult has significantly affected redox homeostasis via depletion of superoxide dismutase, glutathione and enhanced reactive oxygen species generation. It also caused dysregulation in mitochondrial dynamics (fusion, fission proteins), dissipation of mitochondrial transmembrane potential and increased sorbitol accumulation. Finally, apoptosis was observed with upregulation of Bax, activation of caspase-3 and downregulation of Bcl-2. Cinnamic acid cotreatment increased the innate antioxidant status, improved mitochondrial function and prevented apoptosis in H9c2 cardiomyoblasts. Moreover, this in vitro model is found to be ideal for the elucidation of mechanisms at the cellular and molecular level of any physiological, pharmacological and toxicological incidents in H9c2 cells.

Chlorogenic acid attenuates glucotoxicity in H9c2 cells via inhibition of glycation and PKC α upregulation and safeguarding innate antioxidant status

A series of cardiovascular complications associated with hyperglycemia is a critical threat to the diabetic population. Here we elucidate the link between hyperglycemia and cardiovascular diseases onset, focusing on oxidative stress and associated cardiac dysfunctions. The contribution of advanced glycation end products (AGE) and protein kinase C (PKC) signaling is extensively studied. For induction of hyperglycemia, H9c2 cells were incubated with 33 mM glucose for 48 h to simulate the diabetic condition in in vitro system. Development of cardiac dysfunction was confirmed with the significant increase of lactate dehydrogenase (LDH) release to the medium and associated decrease in cell viability. Various parameters like free radical generation, alteration in innate antioxidant system, lipid peroxidation, AGE production and PKC α -ERK axis were investigated during hyperglycemia and with chlorogenic acid. Hyperglycemia has significantly enhanced reactive oxygen species (ROS- 4 fold) generation, depleted SOD activity (1.3 fold) and expression of enzymes particularly CuZnSOD (SOD1) and MnSOD (SOD2), increased production of AGE (2.18 fold). Besides, PKC α dependent ERK signaling pathway was found activated (1.43 fold) leading to cardiac dysfunction during hyperglycemia. Chlorogenic acid (CA) was found beneficial against hyperglycemia most probably through its antioxidant mediated activity. The outcome of this preliminary study reveals the importance of integrated approach emphasizing redox status, glycation and signaling pathways like PKC α - ERK axis for control and management of diabetic cardiomyopathy (DCM) and potential of bioactives like CA.

Attenuation of arsenic trioxide induced cardiotoxicity through flaxseed oil in experimental rats

OBJECTIVES

Arsenic trioxide (As₂O₃) is a potent drug for acute promyelocytic leukaemia, but its clinical trials are allied with some serious adverse events mainly cardiac functional abnormalities. So the objective of our investigation is to identify the cardioprotective action of flaxseed oil (FSO), a natural compound against As₂O₃ induced cardiotoxicity.

METHODS

Male wistar rats were treated with As₂O₃ (4 mg/kg) to induce cardiotoxicity. FSO (250 and 500 mg/kg) was given in combination with As₂O₃ for evaluating its cardioprotective efficacy.

RESULTS

Treatment with As₂O₃ resulted in deposition of arsenic in heart tissue, increased cardiac marker enzymes release, lipid peroxidation (LPO), oxidative insults and pathological damages in the heart. Co-treatment with FSO (500 mg/kg) significantly reduced the arsenic accumulation, cardiac marker enzymes, LPO and cardiac structural alterations. FSO treatment significantly improved cardiac glutathione content, antioxidant enzymes and reduced the pathological damages in cardiac tissue. Gas chromatographic-mass spectrometry analysis revealed that the major fatty acid content in the FSO is alpha-linolenic acid, which has a strong milieu in cardiac health.

CONCLUSION

The results of the current investigation suggested that FSO is an effective agent in reducing arsenic-induced cardiac toxicity and can be used as an adjunct/dietary supplement for the cancer patients on As₂O₃ therapy.

Novel glycoconjugated squaraine dyes for selective optical imaging of cancer cells

Glycoconjugated squaraine dyes for selective internalisation in cancer cell lines are reported. The cancer cell selectivity was achieved through the “Warburg effect”.

Mitochondrial dysfunction in H9c2 cells during ischemia and amelioration with Tribulus terrestris L

AIMS

The present study investigates the protective effect of partially characterized Tribulus terrestris L. fruit methanol extract against mitochondrial dysfunction in cell based (H9c2) myocardial ischemia model.

MAIN METHODS

To induce ischemia, the cells were maintained in an ischemic buffer (composition in mM -137 NaCl, 12 KCl, 0.5 MgCl2, 0.9 CaCl2, 20 HEPES, 20 2-deoxy-d-glucose, pH-6.2) at 37°C with 0.1% O2, 5% CO2, and 95% N2 in a hypoxia incubator for 1h. Cells were pretreated with various concentrations of T. terrestris L. fruit methanol extract (10 and 25μg/ml) and Cyclosporin A (1μM) for 24h prior to the induction of ischemia.

KEY FINDINGS

Different parameters like lactate dehydrogenase release, total antioxidant capacity, glutathione content and antioxidant enzymes were investigated. Studies were conducted on mitochondria by analyzing alterations in mitochondrial membrane potential, integrity, and dynamics (fission and fusion proteins - Mfn1, Mfn2, OPA1, Drp1 and Fis1). Various biochemical processes in mitochondria like activity of electron transport chain (ETC) complexes, oxygen consumption and ATP production was measured. Ischemia for 1h caused a significant (p≤0.05) increase in LDH leakage, decrease in antioxidant activity and caused mitochondrial dysfunction. T. terrestris L. fruit methanol extract pretreatment was found effective in safeguarding mitochondria via its antioxidant potential, mediated through various bioactives. HPLC of T. terrestris L. fruit methanol extract revealed the presence of ferulic acid, phloridzin and diosgenin.

SIGNIFICANCE

T. terrestris L. fruit ameliorate ischemic insult in H9c2 cells by safeguarding mitochondrial function. This validates the use of T. terrestris L. against heart disorders.

Licarin B from Myristica fragrans improves insulin sensitivity via PPARγ and activation of GLUT4 in the IRS-1/PI3K/AKT pathway in 3T3-L1 adipocytes

Licarin B, a major bioactive compound isolated fromMyristica fragransmace improves glucose uptakeviaPPARγ and GLUT4 translocation in IRS-1/PI3K/AKT pathway in adipocytes

Insulin resistance by TNF-α is associated with mitochondrial dysfunction in 3T3-L1 adipocytes and is ameliorated by punicic acid, a PPARγ agonist

Punicic acid (PA), a poly unsaturated fatty acid found abundantly in pomegranate seed oil is reported to have PPARγ agonist property. TNF-α mediated insulin resistance plays an important role in the pathogenesis of diabetes and is associated with severe mitochondrial impairment. In this study, PA was evaluated for its ability to ameliorate TNF-α induced mitochondrial dysfunctions in 3T3-L1 adipocytes. For this, we examined the alterations in mitochondrial energetics, biogenesis, transmembrane potential and dynamics in TNF-α induced insulin resistant model of 3T3-L1 adipocytes. PA improved glucose uptake, ROS accumulation, mitochondrial biogenesis and energetics in TNF-α treated cells. In addition, treatment with PA was found to ameliorate TNF-α induced alterations in proteins associated with mitochondrial dynamics like FIS1 and OPA1. These findings suggest that PA can be considered as an active lead for the management of insulin resistance and associated mitochondrial dysfunctions.

A lysosome-targeted drug delivery system based on sorbitol backbone towards efficient cancer therapy

A straightforward synthetic approach was adopted for the construction of a lysosome-targeted drug delivery system (TDDS) using sorbitol scaffold (Sor) linked to octa-guanidine and tetrapeptide GLPG, a peptide substrate of lysosomal cysteine protease, cathepsin B. The main objective was to efficiently deliver the potential anticancer drug, doxorubicin to the target sites, thereby minimizing dose-limiting toxicity. Three TDDS vectors were synthesized viz., DDS1: Sor-GLPG-Fl, DDS2: Sor-Fl (control) and DDS3: Sor-GLPGC-SMCC-Dox. Dox release from DDS3 in the presence of cathepsin B was studied by kinetics measurement based on the fluorescent property of Dox. The cytotoxicity of DDS1 was assessed and found to be non-toxic. Cellular internalization and colocalization studies of all the 3 systems were carried out by flow cytometry and confocal microscopy utilizing cathepsin B-expressing HeLa cells. DDS1 and DDS3 revealed significant localization within the lysosomes, in contrast to DDS2 (control). The doxorubicin-conjugated carrier, DDS3, demonstrated significant cytotoxic effect when compared to free Dox by MTT assay and also by flow cytometric analysis. The targeted approach with DDS3 is expected to be promising, because it is indicated to be advantageous over free Dox, which possesses dose-limiting toxicity, posing risk of injury to normal tissues.

Bilobalide attenuates hypoxia induced oxidative stress, inflammation, and mitochondrial dysfunctions in 3T3-L1 adipocytes via its antioxidant potential

Excessive expansion of white adipose tissue leads to hypoxia which is considered as a key factor responsible for adipose tissue dysfunction in obesity. Hypoxia induces inflammation, insulin resistance, and other obesity related complications. So the hypoxia-signalling pathway is expected to provide a new target for the treatment of obesity-associated complications. Inhibition or downregulation of the HIF-1 pathway could be an effective target for the treatment of obesity related hypoxia. In the present study, we evaluated the effect of hypoxia on functions of 3T3-L1 adipocytes emphasising on oxidative stress, antioxidant status, inflammation and mitochondrial functions. We have also evaluated the protective role of bilobalide, a bioactive from Gingko biloba, on hypoxia induced alterations. The results revealed that hypoxia significantly altered all the vital parameters of adipocyte biology like HIF-1α expression (103.47% ↑), lactate and glycerol release (184.34% and 69.1% ↑, respectively), reactive oxygen species (ROS) production (432.53% ↑), lipid and protein oxidation (376.6% and 566.6% ↑, respectively), reduction in antioxidant enzymes (superoxide dismutase and catalase) status, secretion of inflammatory markers (TNF-α, IL-6, IL-1β and IFN-γ) and mitochondrial functions (mitochondrial mass, membrane potential, permeability transition pore integrity, superoxide generation). Bilobalide significantly protected adipocytes from adverse effects of hypoxia in a dose-dependent manner by attenuating oxidative stress, inflammation and protecting mitochondria. Acriflavine (HIF-1 inhibitor) was used as positive control. On the basis of this study, a detailed investigation is needed to delineate the mechanism of action of bilobalide to develop it as therapeutic target for obesity.

Nimbolide from Azadirachta indica and its derivatives plus first-generation cephalosporin antibiotics: a novel drug combination for wound-infecting pathogens

We evaluate the in vitro efficacy of nimbolide, desacetylnimbin, and the amide derivatives of nimbolide in combination with first-generation cephalosporin antibiotics against major wound-associated bacterial pathogens.

Synthesis, characterization and evaluation of the antioxidant potential of vanadium encapsulated guar gum nanoparticles

The present study investigated the antioxidant potential of guar gum macroparticles (GGMs), vanadium oxide sulphate (VS) encapsulated guar gum macroparticles (GVMs), guar gum nanoparticles (GGNs), VS encapsulated guar gum nanoparticles (GVNs) and VS. GGNs and GVNs prepared by nanoprecipitation were characterized by SEM (scanning electron microscopy), TEM (transmission electron microscopy) and particle size analysis to confirm the nanostructure of the particles. Particle size analysis revealed that GVNs possess a size of 239 nm, about 148 nm larger than that of GGNs. TEM imaging and EDAX data also confirmed the formation of fine spherical nanoparticles with vanadium incorporation. In addition the larger size of GVNs also confirmed the vanadium incorporation. MTT assay showed that concentrations up to 100 nM of GVNs for 24 h exposure did not induce significant toxicity when VS was toxic (16%) at 100 nM. Various in vitro antioxidant assays (total reducing power, total antioxidant capacity, DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), hydroxyl radical and superoxide anion radical scavenging assays) revealed significantly high antioxidant potential of GVNs compared to GGNs, VS, GGMs and GVMs. The IC50 of GVNs was 23.21 ± 2.1 μg mL(-1), 33.0 ± 2.93 μg mL(-1), 21 ± 1.98 μg mL(-1) and 22.79 ± 2.12 μg mL(-1) for DPPH, ABTS, hydroxyl, superoxide anion scavenging activity assays respectively. The cell line based assay also proved that the GVN was more effective in reactive oxygen species (ROS) scavenging than VS against tertiary butyl hydrogen peroxide (TBHP) induced oxidative stress in H9c2 cell lines. The overall results indicated that vanadium in combination with nano guar gum exhibits significantly high antioxidant potential.

An in vitro study reveals the nutraceutical potential of punicic acid relevant to diabetes via enhanced GLUT4 expression and adiponectin secretion

The prevalence of diabetes and heart diseases is increasing in the world. Nutraceuticals of natural origin are gaining importance as an alternative to modern drugs for the management of metabolic syndrome. In the present study, punicic acid (PA), a major bioactive found in pomegranate seed, was subjected for biological characterization with respect to peroxisome proliferator-activated receptor gamma (PPARγ) agonist property in an in vitro system (3T3-L1 adipocytes). We evaluated the adipogenic potential of various concentrations (5, 10 and 30 μM) of PA by studying triglyceride accumulation and glycerol-3-phosphate dehydrogenase (GPDH) activity in adipocytes, which were found to be increased moderately compared with the positive control, i.e. rosiglitazone (RG). Glucose uptake activity (↑225.93% ± 2.55% for 30 μM of PA), and the prevention of reactive oxygen species (ROS) generation (↓57 ± 1.83% for 30 μM of PA) in adipocytes with PA were also evaluated. We also found that PA increased adiponectin secretion and upregulated GLUT4 expression and translocation in adipocytes. Molecular modelling studies revealed a high binding affinity of PA to the PPARγ ligand binding domain. An in vitro ligand binding assay based on time-resolved fluorescence resonance energy transfer (TR-FRET) also proved PA as a PPARγ agonist. Finally, we conclude that PA is a potential nutraceutical and should be encouraged for use both as a prophylactic and therapeutic agent.

Apigenin and quercetin ameliorate mitochondrial alterations by tunicamycin-induced ER stress in 3T3-L1 adipocytes

Endoplasmic reticulum (ER) is an important organelle with functions like protein synthesis, folding, and calcium homeostasis. ER stress, a condition that dramatically affects protein folding homeostasis in cells, has been associated with a number of metabolic disorders. Emerging clinical and preclinical evidence support the notion that pharmacological modulators of ER stress have therapeutic potential as a novel target for treating metabolic diseases. ER is in physical contact with mitochondria, and there is a strong cross talk between these organelles at functional level. The present investigation was aimed to check the mitochondrial alterations in adipocytes with tunicamycin-induced ER stress and modulation by apigenin and quercetin. For this, differentiated adipocytes were incubated with tunicamycin (2 μg/ml) for 18 h, and changes in mitochondrial membrane potential, biogenesis, reactive oxygen species production, and adiponectin secretion were seen. Tunicamycin-induced ER stress altered reactive oxygen species (ROS) (6.34-fold↑), membrane potential (4.1-fold↑), mitochondrial biogenesis (2.4-fold↓), and adiponectin secretion (3.5-fold↓). Apigenin and quercetin ameliorated alterations in mitochondria. From results, we conclude that ER stress significantly alters mitochondrial functions and both the bioactives significantly protected mitochondrial alterations during ER stressand reestablished adiponectin secretion.

Parmotrema tinctorum exhibits antioxidant, antiglycation and inhibitory activities against aldose reductase and carbohydrate digestive enzymes: an in vitro study

This study evaluated the inhibitory potential of ethyl acetate extract of Parmotrema tinctorum (PTEE), an edible lichen, against aldose reductase (AR) and carbohydrate digestive enzymes such as α-glucosidase and α-amylase. It was also screened for antioxidant activities by using DPPH, ABTS, superoxide and hydroxyl radical-scavenging assays. PTEE exhibited α-glucosidase, α-amylase and AR inhibition along with significant antiglycation potential with an estimated IC50 value of 58.45 ± 1.24, 587.74 ± 3.27, 139.28 ± 2.6 and 285.78 ± 1.287 μg/mL, respectively. Antioxidant activity of PTEE against DPPH (IC50 396.83 ± 2.98 μg/mL), ABTS (151.34 ± 1.79 μg/mL), superoxide (30.29 ± 1.17 μg/mL) and hydroxyl (35.42 ± 1.22 μg/mL) radicals suggests the antioxidant potential of P. tinctorum. Significant antioxidant activity and inhibitory potential against carbohydrate digestive enzymes and AR suggest that P. tinctorum can be developed as functional food/nutraceuticals for diabetes after detailed study.

In vitro antidiabetic and inhibitory potential of turmeric (Curcuma longa L) rhizome against cellular and LDL oxidation and angiotensin converting enzyme

Turmeric (Curcuma longa L) rhizome extracts were evaluated for their antidiabetic, antihypertensive and antioxidant potentials. α-Glucosidase (0.4 μg/mL) and α-amylase (0.4 μg/mL) inhibitory potential of turmeric ethyl acetate extract was significantly higher than those of the reference drug acarbose (17.1 μg/mL and 290.6 μg/mL respectively). Protein glycation inhibitory potential of ethyl acetate extract was 800 times higher than that of ascorbic acid. High potential of ethyl acetate extract to scavenge free radicals and to reduce LDL oxidation and cellular oxidative stress was also revealed. The positive correlation obtained between the free radical scavenging capacity of the extracts and their antiglycation potential further confirmed the role of antioxidants in controlling glycation reactions. Ethyl acetate extract was also found as effective in reducing hypertension by inhibiting angiotensin converting enzyme (ACE). Antidiabetic, ACE inhibitory and antioxidant capacities of the extracts were in the order of their curcumin contents.

Inhibitory effect of Terminalia chebula Retz. fruit extracts on digestive enzyme related to diabetes and oxidative stress

Terminalia chebula fruit extracts were prepared sequentially with hexane, ethyl acetate, methanol and methanol-water (70:30) and tested for their α-glucosidase inhibitory and antioxidant potential. The study resulted in the formulation of an extract with high α-glucosidase inhibitory potential (IC(50) 0.19 ± 0.03 µg mL(-1)) enriched with hydrolysable tannins. Also, each of the extract was chemically characterized by reversed-phase high-performance liquid chromatography on the basis of their marker compounds chebulagic acid, chebulinic acid and corilagin in order to give explanation to the significant activity shown by the extracts. The antioxidant potential of the highly active extract was evaluated in the cellular level also using superoxide dismutase, glutathione S-transferase and induced oxidative stress assays. The results indicated the possibility of using the extract as a nutraceutical health supplement in the management of type 2 diabetes.

Antioxidant, antiglycation and inhibitory potential of Saraca ashoka flowers against the enzymes linked to type 2 diabetes and LDL oxidation

OBJECTIVE

The present study investigated the antioxidant, antiglycation and inhibitory potential of flavonoid fraction of Saraca ashoka flowers (SAF) against alpha-glucosidase and alpha-amylase (the enzymes linked to type 2 diabetes) and LDL oxidation.

MATERIALS AND METHODS

Antioxidant capacity of SAF was evaluated by estimating total antioxidant activity (TAA) and its protective effects against the oxidative stress induced by H2O2 on C2C12 cells. Cytotoxicity by MTT assay and markers of oxidative stress: reduced glutathione (GSH), malondialdehyde (MDA) and reactive oxygen species (ROS) were measured.

RESULTS

Pre-treatment of C2C12 cells with SAF prevented the increased formation of MDA and depletion of GSH induced by H2O2. The increased ROS generation induced by H2O2 was also reduced by a pretreatment with SAF. Significant inhibitory potential against alpha-glucosidase and alpha-amylase enzymes revealed the therapeutic potential of SAF as an antihyperglycemic agent. SAF also demonstrated potent antiglycation property and inhibited LDL oxidation under in vitro conditions.

CONCLUSIONS

The overall results demonstrate that SAF can be used as an ideal natural remedy for preventing oxidative stress and other complications associated with diabetes.

Turmerin, the antioxidant protein from turmeric (Curcuma longa) exhibits antihyperglycaemic effects

A wide range of proteinaceous inhibitors are present in plants to protect themselves from hydrolytic enzymes. In this study, turmerin, a water-soluble peptide in turmeric rhizomes, was evaluated for its inhibitory potential against glucosidase and its antioxidant (AO) capacity. Turmerin inhibited α-amylase and α-glucosidase activities with IC₅₀ values 31 and 192 µg mL⁻¹, respectively. Under the experimental conditions, those values for a standard glucosidase inhibitor, acarbose, were 81 and 296 µg mL⁻¹, respectively. The AO capacity of turmerin was evaluated using in vitro assay systems. Turmerin showed good DPPH (IC₅₀ = 29 µg mL⁻¹) and superoxide (IC₅₀ = 48 µg mL⁻¹) and moderate ABTS (IC₅₀ = 83 µg mL⁻¹) radical scavenging and Fe(II) chelation (IC₅₀ = 101 µg mL⁻¹) capacities. The inhibitory potential showed by turmerin against enzymes linked to type 2 diabetes, as well as its moderate AO capacity, could rationalise the traditional usage of turmeric rhizome preparations against diabetes.

Inhibitory potential of ginger extracts against enzymes linked to type 2 diabetes, inflammation and induced oxidative stress

Ginger (Zingiber officinale Roscoe) continues to be used as an important cooking spice and herbal medicine around the world. Gingerols, the major pungent components of ginger, are known to improve diabetes, including the effect of enhancement against insulin sensitivity. In the current study, ginger sequentially extracted with different solvents-namely, hexane, ethyl acetate, methanol, 70% methanol-water and water-were screened to determine the variations in phenolic-linked active constituents. The potential of these extracts to inhibit key enzymes relevant to type 2 diabetes and inflammation was studied. Phenolic compounds-namely, gingerols and shoagols-were quantified using high-performance liquid chromatography. Ethyl acetate extract showed higher activity compared with other extracts. These studies indicate that ginger has very good potential for α-glucosidase and α-amylase inhibition relevant for type 2 diabetes management and cyclooxygenase inhibition for inflammation.

In vitro antioxidant and inhibitory potential of Terminalia bellerica and Emblica officinalis fruits against LDL oxidation and key enzymes linked to type 2 diabetes

The present study evaluated the free radical scavenging capacity and antioxidant potential of different solvent extracts (Hexane (HE), ethyl acetate (EA), methanol (ME), 70% methanol (MW) and Water (WA)) of Terminalia bellerica (TB) and Emblica officinalis (EB) fruits. Methanol extract (ME) of TB and EB fruits exhibited maximum scavenging activity against DPPH, superoxide, hydroxyl and nitric oxide radicals. Cell based antioxidant activity was assayed by flow cytometry using DCFH-DA as probe. Methanol extracts were also screened for their antidiabetic activity via inhibition of α-amylase, α-glucosidase and antiglycation assays. Results showed that ME of TB and EB can act as potent α-amylase and α-glucosidase inhibitor. Significant antiglycation activity also confirms the therapeutic potential of these extracts against diabetes. Both the extracts significantly inhibited the oxidation of LDL under in vitro conditions. Liquid chromatography-mass spectroscopy (LC-MS) analysis revealed that methanol extract of TB and EB contains ellagic acid and ascorbic acid as the major compound respectively.

Evaluation of adverse cardiac effects induced by arsenic trioxide, a potent anti-APL drug

Arsenic trioxide (ATO/As2O3) is a promising drug for patients with a relapse of acute promyelocytic leukemia (APL); however, it frequently causes fatal arrhythmias. This study aims to investigate the various cellular and molecular mechanisms of adverse cardiac effects and the electrophysi-ological alterations caused by As2O3. We show the dose-dependent effect of ATO (0.2, 0.4, 0.8, 1.6, 3.2, 6.4 mum) on electrically driven cardiac action potential from the papillary muscle of the guinea pig. ATO causes a significant prolongation of action potential duration (APD) at various levels of repolarization, conduction delay, and increased triangulation, which is a novel marker for the proarrhythmic potential of a compound. Electrolyte imbalance (hypomagnesemia and hypokalemia) has also been found to cause amplification of ATO toxicity. Since ion channels play a very important role in the generation of cardiac action potential, we used various ion channel modulators such as choline, minoxidil, nifedipine, and verapamil to determine whether these agents could antagonize electrophysiological alterations caused by ATO. In in vivo experiments, ATO administration to animals for 10 days caused myocardial disorganization, interstitial edema and infiltration of inflammatory cells in the heart. Efforts were also made to screen the efficacy of vitamin C against ATO toxicity. ATO also caused a significant increase in the activity of certain clinically relevant enzymes for cardiac function and antioxidant mechanismssuch as serum creatine kinase isoenzyme, lactate dehydrogenase, glutathione peroxidase and reduced glutathione. In conclusion, ATO causes significant adverse cardiac effects and we suggest that cardiac function to be monitored during treatment with ATO. Our results also indicate that the status of the body's main electrolyte content (such as magnesium and potassium) is also an influencing factor on the magnitude of toxicity of arsenic trioxide.

Characterization of cytotoxicity induced by arsenic trioxide (a potent anti-APL drug) in rat cardiac myocytes

Arsenic, a known environmental toxicant, is ubiquitously present in the environment. Arsenic trioxide (ATO), an anti-acute promyelocytic leukemia (APL) drug, is associated with cardiac toxicity. It is reported to induce cardiac arrhythmia via altering various ion channels involved in the repolarization phase of cardiac action potential. The exact molecular mechanism of cardiovascular adverse effect due to ATO exposure has not been fully elucidated except for alteration on ion channels. To evaluate the cytotoxic effect of ATO on cardiac myocytes, primary culture of myocytes was treated with different doses (30, 60 and 90 microM) of ATO for various periods (24, 48 and 72 h). Cardiac toxicity was assessed by monitoring cell viability, mitochondrial and deoxyribonucleic acid (DNA) integrity, reactive oxygen species (ROS) generation, calcium overload and apoptosis. ATO exposure caused alteration in mitochondrial integrity, generation of ROS, calcium overload and apoptosis in cardiac cells in dose- and duration-dependent manner. There was no DNA fragmentation. Hence our results show that ATO causes apoptosis in cardiomyocytes by generation of ROS and the induction of calcium overload.

Acanthocheilonema viteae: octopamine and its physiological role

Octopamine acts as an important neurotransmitter and neuromodulator in arthropods, mollusks, and nematodes. In mammals, however, no definite function for this amine has yet been described. By virtue of this difference in the neurophysiological requirement of the mammalian host and nematodes, octopamine offers good opportunity for exploring this area deeply with a view to identify a unique target for filarial chemotherapy. Results of the present study indicated that Acanthocheilonema viteae, the rodent filarial parasite, utilized tyrosine as a precursor for producing octopamine and some other biogenic amines. Octopamine exhibited specific saturable binding with the membrane prepared from the anterior portion of the filariid. This amine induced concentration dependent increase in the membrane potential which possibly caused tonic paralysis of the filariid. The rate of micro filarial release by the female worms also declined in the presence of this amine. The study thus provided preliminary evidences for the presence of an octopamine neurotransmitter system and also about some of the roles it plays in A. viteae.

Frequency- and time-dependent effects of fendiline on action potentials of guinea pig papillary muscle

The action of fendiline on cardiac electrical activity was investigated in guinea pig papillary muscle by monitoring frequency- and time-dependent changes in membrane potential, action potential (AP) configuration and conduction velocity. Isolated guinea pig papillary muscles driven at 0.1 to 3 Hz showed a concentration-dependent reduction of +Vmax, overshoot, and AP duration at -20mV (APD20) in the presence of fendiline (1-320 microM), reflecting inhibition of Na+ and L-type Ca2+ channels, respectively. No significant change in resting potential and AP duration at 90% repolarization (APD90) were observed. Inhibition of +Vmax and APD20 was more prominent at higher frequency of stimulation (2 Hz) than at lower ones (0.2 Hz), demonstrating frequency-dependent block of Na+ and Ca2+ channels including an open channel block. A good relationship between changes in +Vmax and APD20 suggested some commonality in the mechanism of inhibition of Na+ and Ca2+ channels by fendiline. Time-dependence of effects of fendiline, observed in presence of bolus dose (200 microM), showed an earlier onset of inhibition of +Vmax and APD20, particularly at higher frequencies. Missed beats and conduction block also appeared earlier in preparations driven at higher frequency. These findings suggest a frequency-dependent (and open channel) block of Na+ and Ca2+ channels by fendiline, leading to inhibition of fast and slow conduction in addition to its reported inactivated Ca2+ channel block.

Kinetic studies of purified malate dehydrogenase in liver of streptozotocin-diabetic rats and the effect of leaf extract of Aegle marmelose (L.) Correa ex Roxb

The functional basis of diabetes-mellitus to a certain extent, can be elucidated by studying diabetes-induced changes in metabolic enzymes. Malate dehydrogenase (MDH), is an enzyme directly involved in glucose metabolism. The kinetic parameters of MDH and its purified cytosolic isozyme, S-MDH, have been studied in the liver of streptozotocin-diabetic rats; also the potential of the leaf extract of A. marmelose as an anti-diabetic agent was investigated. The Km of the liver enzyme increased significantly, in both crude and purified preparations in the diabetic state when compared to the respective controls. Insulin as well as leaf-extract treatment of the diabetic rats brought about a reversal of Km values to near normal. Vmax of purified S-MDH was significantly higher in the diabetic state when compared to the control. Insulin and leaf extract treatment did not reverse this change. Since MDH is an important enzyme in glucose metabolism, the variation in its quantitative and qualitative nature may contribute to the pathological status of diabetes. The fact that leaf extract of A. marmelose was found to be as effective as insulin in restoration of blood glucose and body weight to normal levels, the use of A. marmelose as potential hypoglycemic agent is suggested.