Mahesh Subramanian

Antioxidant properties of a Tinospora cordifolia polysaccharide against iron-mediated lipid damage and γ-ray induced protein damage

Abstract The antioxidant activity of an arabinogalactan polysaccharide (TSP) isolated from Tinospora cordifolia, an Indian medicinal plant, was studied. The polysaccharide showed good protection against iron-mediated lipid peroxidation of rat brain homogenate as revealed by the thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxide (LOOH) assays. TSP also provided significant protection to protein against γ-ray induced damage. The protective action can possibly be explained by its very high reactivity towards DPPH, superoxide radicals and the most damaging of radicals, the hydroxyl radical.

MADD, a Splice Variant of IG20, Is Indispensable for MAPK Activation and Protection against Apoptosis upon Tumor Necrosis Factor-α Treatment

We investigated the physiological role of endogenous MAPK-activating death domain-containing protein (MADD), a splice variant of the IG20 gene, that can interact with TNFR1 in tumor necrosis factor-α (TNFα)-induced activation of NF-κB, MAPK, ERK1/2, JNK, and p38. Using exon-specific short hairpin RNAs expressing lentiviruses, we knocked down the expression of all IG20 splice variants or MADD, which is overexpressed in cancer cells. Abrogation of MADD expression rendered cells highly susceptible to TNFα-induced apoptosis in the absence of cycloheximide. It also resulted in a dramatic loss in TNFα-induced activation of MAPK without any apparent effect on NF-κB activation. This observation was substantiated by an accompanying loss in the activation of p90RSK, a key downstream target of MAPK, whereas the NF-κB-regulated interleukin 6 levels remained unaffected. Endogenous MADD knockdown, however, did not affect epidermal growth factor-induced MAPK activation thereby demonstrating the specific requirement of MADD for TNF receptor-mediated MAPK activation. Re-expression of short hairpin RNA-resistant MADD in the absence of endogenous IG20 expression rescued the cells from TNFα-induced apoptosis. The requirement for MADD was highly specific for TNFα-induced activation of MAPK but not the related JNK and p38 kinases. Loss of MADD expression resulted in reduced Grb2 and Sos1/2 recruitment to the TNFR1 complex and decreased Ras and MEKK1/2 activation. These results demonstrate the essential role of MADD in protecting cancer cells from TNFα-induced apoptosis by specifically activating MAPKs through Grb2 and Sos1/2 recruitment, and its potential as a novel cancer therapeutic target.

MADD, a splice variant of IG20, is indispensable for MAPK activation and protection against apoptosis upon TNFα treatment

We investigated the physiological role of endogenous MAPK-activating death domain-containing protein (MADD), a splice variant of the IG20 gene, that can interact with TNFR1 in tumor necrosis factor-α (TNFα)-induced activation of NF-κB, MAPK, ERK1/2, JNK, and p38. Using exon-specific short hairpin RNAs expressing lentiviruses, we knocked down the expression of all IG20 splice variants or MADD, which is overexpressed in cancer cells. Abrogation of MADD expression rendered cells highly susceptible to TNFα-induced apoptosis in the absence of cycloheximide. It also resulted in a dramatic loss in TNFα-induced activation of MAPK without any apparent effect on NF-κB activation. This observation was substantiated by an accompanying loss in the activation of p90RSK, a key downstream target of MAPK, whereas the NF-κB-regulated interleukin 6 levels remained unaffected. Endogenous MADD knockdown, however, did not affect epidermal growth factor-induced MAPK activation thereby demonstrating the specific requirement of MADD for TNF receptor-mediated MAPK activation. Re-expression of short hairpin RNA-resistant MADD in the absence of endogenous IG20 expression rescued the cells from TNFα-induced apoptosis. The requirement for MADD was highly specific for TNFα-induced activation of MAPK but not the related JNK and p38 kinases. Loss of MADD expression resulted in reduced Grb2 and Sos1/2 recruitment to the TNFR1 complex and decreased Ras and MEKK1/2 activation. These results demonstrate the essential role of MADD in protecting cancer cells from TNFα-induced apoptosis by specifically activating MAPKs through Grb2 and Sos1/2 recruitment, and its potential as a novel cancer therapeutic target.

Antioxidant and radioprotective properties of an Ocimum sanctum polysaccharide

Abstract The antioxidant activity of two polysaccharides isolated from the Indian medicinal plants, Ocimum sanctum and Tinospora malabarica, was studied. Only the O. sanctum polysaccharide (OSP) showed significant activity. OSP could prevent oxidative damage to liposomal lipids and plasmid DNA induced by various oxidants such as iron, AAPH and γ-radiation, besides scavenging important ROS such as the superoxide radical and hydrogen peroxide and inhibiting xanthine oxidase. In addition, OSP could prevent γ-radiation-mediated cell deaths in mouse splenocytes.

Resveratrol induced inhibition of Escherichia coli proceeds via membrane oxidation and independent of diffusible reactive oxygen species generation.

Resveratrol (5-[(E)-2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol), a redox active phytoalexin with a large number of beneficial activities is also known for antibacterial property. However the mechanism of action of resveratrol against bacteria remains unknown. Due to its extensive redox property it was envisaged if reactive oxygen species (ROS) generation by resveratrol could be a reason behind its antibacterial activity. Employing Escherichia coli as a model organism we have evaluated the role of diffusible reactive oxygen species in the events leading to inhibition of this organism by resveratrol. Evidence for the role of ROS in E. coli treated with resveratrol was investigated by direct quantification of ROS by flow cytometry, supplementation with ROS scavengers, depletion of intracellular glutathione, employing mutants devoid of enzymatic antioxidant defences, induction of adaptive response prior to resveratrol challenge and monitoring oxidative stress response elements oxyR, soxS and soxR upon resveratrol treatment. Resveratrol treatment did not result in scavengable ROS generation in E. coli cells. However, evidence towards membrane damage was obtained by potassium leakage (atomic absorption spectrometry) and propidium iodide uptake (flow cytometry and microscopy) as an early event. Based on the comprehensive evidences this study concludes for the first time the antibacterial property of resveratrol against E. coli does not progress via the diffusible ROS but is mediated by site-specific oxidative damage to the cell membrane as the primary event.

Induction of apoptosis in human cancer cells by a Bacillus lipopeptide bacillomycin D

A newly isolated and characterized Bacillus amyloliquefaciens strain fiply 3A has been found to produce an extracellular cyclic lipopeptide which structurally resembled bacillomycin D, earlier reported to be produced by Bacillus subtilis. The lipopeptide showed a dose dependent killing of three different human cancer cell lines viz. A549 (alveolar adenocarcinoma), A498 (renal carcinoma) and HCT-15 (colon adenocarcinoma), while not affecting the normal cell line L-132 (pulmonary epithelial cells) when analyzed using MTT assay and FACS analysis. Staining the cells with H2-DCFDA showed an increase in reactive oxygen species (ROS) formation in the lipopeptide treated cell population. Hoechst 33342 staining of nuclei further indicated apoptosis as a major mechanism of cell death in lipopeptide treated cells and the typical symptoms of apoptosis including cell shrinkage, nuclear condensation and fragmentation of nuclei were observed. Lipopeptide treatment induced extensive DNA damage in the treated cells, which was indicated by a TUNEL assay. Flow cytometric analysis exhibited lipopeptide concentration dependent apoptosis which was further confirmed during clonogenic assay of the lipopeptide treated cells.

DL-trans-3,4-Dihydroxy-1-selenolane (DHSred) accelerates healing of indomethacin-induced stomach ulceration in mice

Abstract Management of the gastro-toxicity of non-steroidal anti-inflammatory drugs (NSAIDs) remains a crucial problem, because the commercially available anti-ulcer drugs have side effects and are often expensive. Hence, the potential of a new water-soluble GPx mimic, DL-trans-3,4-dihydroxy-1-selenolane (DHSred) in healing the indomethacin-induced stomach ulceration in mice was examined. Administration of indomethacin (18 mg/kg, p. o.) induced ulceration in the glandular portion of the gastric mucosa, accompanied by increased lipid peroxidation (1.3-fold, p <0.001) and protein oxidation (1.5-fold, p < 0.001), depletion of thiol-defense (42.5%, p < 0.01), plasma total antioxidant status (53.4%, p < 0.001) and mucin (47.5%, p < 0.01), as well as reduced expressions of cyclooxygenases and prostaglandin synthesis (54.7%, p < 0.001) in the gastric tissues of mice. Daily oral administration of DHSred (2.5 mg/kg) or omeprazole (Omez) (3 mg/kg) for 3 days respectively produced ˜74% and 69% (p < 0.001) healing of the acute gastric ulceration. The test samples also significantly reversed all the adverse effects of indomethacin on the biochemical parameters. Apparently, the gastric ulcer healing action of DHSred and Omez was due to their antioxidant action and their ability to protect mucin and augment PG synthesis by upregulation of the COX isozymes. The results suggested that the non-toxic and inexpensive compound, DHSred, may be a good candidate for further evaluation as a potent anti-ulcer drug.

dl-trans-3,4-Dihydroxy-1-selenolane (DHSred) heals indomethacin-mediated gastric ulcer in mice by modulating arginine metabolism

BACKGROUND The importance of the arginine metabolism in gastric ulcer-healing is given relatively less attention. Hence the role of controlling this pathway by dl-trans-3,4-dihydroxy-1-selenolane (DHSred) and omeprazole against indomethacin-induced stomach ulceration in mouse was investigated. METHODS Swiss albino mice were ulcerated with indomethacin followed by treatment with the test samples, and the activities of myeloperoxidase (MPO), total nitric oxide synthase (NOS) and arginase, the expressions of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS), and the pro-/anti-inflammatory cytokine levels were assayed. NOS-inhibitors were also used to establish the biochemical mechanism. RESULTS Indomethacin induced maximum ulceration in mice on the 3rd day, associated with reduced arginase activity, eNOS expression, along with increased MPO and total NOS activities, nitric oxide (NO) generation, iNOS expression, and pro-/anti-inflammatory (Th1/Th2) cytokine ratio. Treatment with DHSred (2.5mgkg(-1)×3days) restored the cytokine balance to shift the iNOS/NO axis to the arginase/polyamine axis as revealed from the increased arginase activity and eNOS expression, and reduced iNOS expression, total NOS activity and NO level. CONCLUSIONS The ulcer-healing property of DHSred, but not of omeprazole was due to a favorable pro-/anti-inflammatory cytokine ratio that shifted the arginine metabolism to the polyamine pathway and increased the eNOS/iNOS ratio. The healing action of omeprazole was not significantly associated with these parameters. GENERAL SIGNIFICANCE The shift in the ariginine-metabolism from the iNOS/NO axis to the arginase/polyamine axis is guided by Th1/Th2 cytokines ratio and plays an important role in gastric ulcer-healing. The favourable effects of the non-toxic and water-soluble compound, DHSred on these pathways and other COX-dependent and antioxidative parameters suggested it to be a promising anti-ulcer formulation for further studies.

Divergent synthesis of 4-epi-fagomine, 3,4-dihydroxypipecolic acid, and a dihydroxyindolizidine and their β-galactosidase inhibitory and immunomodulatory activities.

A divergent asymmetric synthesis of the titled iminosugars has been formulated starting from a chiral homoallyl alcohol as the versatile intermediate. The homoallyl alcohol was prepared by a highly diastereoselective Barbier reaction on a d-glucose-derived aldehyde. The protection of its hydroxyl function followed by reductive ozonolysis of the olefin and a subsequent one-pot three-step protocol involving a Staudinger reaction, reductive amination, and benzyloxy carbonyl protection yielded an important bicyclic furanopiperidine derivative. This was converted to the target compounds by following standard reactions. Among the synthesized compounds, 4-epi-fagomine (2b) was the best β-galactosidase inhibitor, and it also prevented LPS-mediated activation of Raw 264.7 macrophage cells. Its congener, 3,4-dihydroxypipecolic acid (4b) also showed similar trends in its cytokine- and enzyme-inhibitory properties at a low concentration (10 μM) but was proinflammatory at higher concentrations. The bicyclic compound dihydroxyindolizidine (21) reduced the proinflammatory cytokine (IL-1β and TNF-α) levels in the LPS-activated Raw 264.7 cells without showing any enzyme-inhibition activity.

Preparation, characterisation and performance evaluation of anti-biofouling property of carbon nanotube-polysulfone nanocomposite membranes

Membrane based process assumes a significant importance among all the separation practices being followed in the present time. Among the limitations faced by the membrane process, the most critical one is the bio-fouling, which results in lesser throughput as well as deterioration in membrane life. To enhance the anti-biofouling behaviour of the membrane surface, nanostructured materials offer a tremendous opportunity. One potential candidate among them is the carbon nanotubes (CNTs). With the objective of having improvement over the existing anti-biofouling tendency of polysulfone membranes, nanocomposites were developed with impregnation of both single walled as well as multi walled CNTs. The performance of the membranes was evaluated in terms of pure water permeability and solute rejection studies. The membranes were characterised using scanning electron microscopy, atomic force microscopy and contact angle studies. The anti-biofouling performance of the membrane surfaces was examined using E. Coli culture and a comparison of antibiofouling tendency obtained with the nanocomposites over the pure polysulfone membranes has been made. It was confirmed that membranes with impregnation of single walled CNTs possess better antibiofouling behaviour as compared to pure polysulfone as well as polysulfone membrane embedded with multi walled CNTs.