Formulation and development of floating capsules of celecoxib: In vitro and in vivo evaluation

The objective of the present study was to develop a hydrodynamically balanced system for celecoxib as single-unit floating capsules. Various grades of low-density polymers were used for formulation of these capsules. The capsules were prepared by physical blending of celecoxib and the polymer in varying ratios. The formulation was optimized on the basis of in vitro buoyancy and in vitro release in citrate phosphate buffer pH 3.0 (with 1% sodium lauryl sulfate). Capsules prepared with polyethylene oxide 60K and Eudragit RL100 gave the best in vitro percentage release and were used as the optimized formulation. By fitting the data into zero-order, first-order, and Higuchi models, we concluded that the release followed zero-order kinetics, as the correlation coefficient (R value) was higher for zero-order release. For gamma scintigraphy studies, celecoxib was radiolabeled with technetium-99m by the stannous reduction method. To achieve the maximum labeling efficiency the process was optimized by studying the reaction at various pH conditions and stannous concentration levels. The radiolabeled complex was added to the optimized capsule, and dissolution studies were performed to ensure that there was no leaching of radioactivity from the capsules. Gamma imaging was performed in rabbits to assess the buoyancy of the optimized formulation. The optimized formulation remained buoyant during 5 hours of gamma scintigraphic studies in rabbits.     

Preconditioning the hyperlipidemic myocardium: fact or fantasy?

Ischemic heart disease is a leading cause of death worldwide. Myocardial ischemia results in reduced coronary flow, followed by diminished oxygen and nutrient supply to the heart. Reperfusion to an ischemic myocardium often augments the ischemic damage, known as ischemia-reperfusion (I/R) injury. Number of studies demonstrated that the hyperlipidemic myocardium is rather sensitive and more vulnerable to I/R-induced myocardial injury. Repeated brief ischemia and reperfusion cycles, termed as ischemic preconditioning, given before a sustained ischemia is known to reduce myocardial damage occur as a result of I/R. A plethora of evidence supports the fact that preconditioning is one of the promising interventional strategies having an ability to limit I/R-induced myocardial injury. Despite this fact, the preconditioning-mediated cardioprotection is blunted in chronic hyperlipidemic condition. This suggests that preconditioning is moderately a ‘healthy heart protective phenomenon’. The mechanisms by which chronic hyperlipidemia abrogates cardioprotective effects of preconditioning are uncertain and are not completely understood. The impaired opening of mitochondrial-K_ATP channels, eNOS uncoupling and excessive generation of superoxides in the hyperlipidemic myocardium could play a role in attenuating preconditioning-mediated myocardial protection against I/R injury. Moreover, hyperlipidemia-induced loss of cardioprotective effect of preconditioning is associated with redistribution of both sarcolemmal and mitochondrial Connexin 43. We addressed, in this review, the potential mechanisms involved in hyperlipidemia-induced impairment of myocardial preconditioning. Additionally, novel pharmacologic interventions to attenuate hyperlipidemia-associated exaggerated I/R-induced myocardial injury have been discussed.     

Tumor necrosis factor alpha induces spermidine/spermine N1-acetyltransferase through nuclear factor kappaB in non-small cell lung cancer cells

Tumor necrosis factor alpha (TNFalpha) is a potent pleiotropic cytokine produced by many cells in response to inflammatory stress. The molecular mechanisms responsible for the multiple biological activities of TNFalpha are due to its ability to activate multiple signal transduction pathways, including nuclear factor kappaB (NFkappaB), which plays critical roles in cell proliferation and survival. TNFalpha displays both apoptotic and antiapoptotic properties, depending on the nature of the stimulus and the activation status of certain signaling pathways. Here we show that TNFalpha can lead to the induction of NFkappaB signaling with a concomitant increase in spermidine/spermine N(1)-acetyltransferase (SSAT) expression in A549 and H157 non-small cell lung cancer cells. Induction of SSAT, a stress-inducible gene that encodes a rate-limiting polyamine catabolic enzyme, leads to lower intracellular polyamine contents and has been associated with decreased cell growth and increased apoptosis. Stable overexpression of a mutant, dominant negative IkappaBalpha protein led to the suppression of SSAT induction by TNFalpha in these cells, thereby substantiating a role of NFkappaB in the induction of SSAT by TNFalpha. SSAT promoter deletion constructs led to the identification of three potential NFkappaB response elements in the SSAT gene. Electromobility shift assays, chromatin immunoprecipitation experiments and mutational studies confirmed that two of the three NFkappaB response elements play an important role in the regulation of SSAT in response to TNFalpha. The results of these studies indicate that a common mediator of inflammation can lead to the induction of SSAT expression by activating the NFkappaB signaling pathway in non-small cell lung cancer cells.     

Regulatory role of iron and EDTA in the shoot development from the epicotyl explants of Syzygium cuminii

Iron has proved to be an integral component of the culture medium supporting the caulogenic response of the epicotyl segments of S. cuminii. In the absence of both the iron and EDTA even the shoot buds failed to develop, while in the presence of either of these, though the shoot buds developed, their elongation was adversely affected. Among the three iron sources tested, ferrous sulphate proved to be the best, as the ferric chloride was not as effective as the former when used either alone or along with EDTA. Ferric citrate, on the other hand, when provided alone, elicited better response than that induced by ferrous sulphate alone. However, in combination with EDTA, the response declined significantly. The estimation of endogenous levels of iron in the explants further supported these results. The quantum of iron absorption was at a maximum during the first week of the culture and the explants, once deprived of iron during the first week, failed to catch up to the level of iron accumulated in the explants maintained continuously on complete medium, even after transfer to the complete medium. Likewise, the level of copper ions did not come up to comparable levels even if the explants were transferred to the complete medium after initial deprivation.     

Changes in sialic acid and fucose contents of enterocytes across the crypt-villus axis in developing rat intestine

Alterations in sialic acid and fucose contents of different populations of epithelial cells have been studied in suckling and adult rat intestine. The progression of cells from crypt base to villus tip is associated with an increase in sialic acid and a decrease in fucose levels of the cells in adult rats. In suckling pups, sialic acid is uniformly distributed along the length of villi, and fucose is richly (P less than 0.01) present in cryptic cells compared to that at the villus tip. Adult-type changes in sialylation and fucosylation of enterocytes across the crypt-villus axis were precociously produced by cortisone administration to suckling pups. Thyroxine treatment was less effective in influencing the glycosylation process in rat intestine.     

NAD+ supplementation prevents STING‐induced senescence in ataxia telangiectasia by improving mitophagy

Senescence phenotypes and mitochondrial dysfunction are implicated in aging and in premature aging diseases, including ataxia telangiectasia (A‐T). Loss of mitochondrial function can drive age‐related decline in the brain, but little is known about whether improving mitochondrial homeostasis alleviates senescence phenotypes. We demonstrate here that mitochondrial dysfunction and cellular senescence with a senescence‐associated secretory phenotype (SASP) occur in A‐T patient fibroblasts, and in ATM‐deficient cells and mice. Senescence is mediated by stimulator of interferon genes (STING) and involves ectopic cytoplasmic DNA. We further show that boosting intracellular NAD⁺ levels with nicotinamide riboside (NR) prevents senescence and SASP by promoting mitophagy in a PINK1‐dependent manner. NR treatment also prevents neurodegeneration, suppresses senescence and neuroinflammation, and improves motor function in Atm^−/− mice. Our findings suggest a central role for mitochondrial dysfunction‐induced senescence in A‐T pathogenesis, and that enhancing mitophagy as a potential therapeutic intervention.     

Nitric Oxide Induces Flowering in the Duckweed Lemna aequinoctialis Welw. (Syn. L. paucicostata Hegelm.) Under Noninductive Conditions

Nitric oxide (NO) plays diverse roles in the growth and development of plants and in their responses to various abiotic and biotic stresses. It has also been reported to repress flowering in Arabidopsis thaliana. In the present study, NO donors sodium nitroprusside (SNP), S-nitroso-N-acetyl penicillamine (SNAP), and 3-morpholinosydnonimine (SIN-1) induced flowering in Lemna aequinoctialis 6746 (a short-day strain) and in L. aequinoctialis LP₆ (a photoperiod-insensitive strain) under noninductive conditions. Nitrate and nitrite, two stable metabolites of NO, did not induce flowering. On the other hand, cyanide donors potassium ferricyanide {K₃[Fe(CN)₆]} and potassium cyanide (KCN) induced flowering in both strains under noninductive conditions. The flowering induced under a 8-h daily photoperiod regime in the short-day strain L. aequinoctialis 6746 was inhibited by NO and cyanide donors. Vegetative multiplication of both strains was adversely affected by NO and cyanide donors, irrespective of the photoperiod conditions. The observed effects of NO donors on flowering were substantially negated by NO scavengers c-PTIO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide] and methylene blue. This confirmed the role of NO in induction of flowering. The inductive effect of CN⁻ also appeared to be partly mediated through NO as NO scavengers partially negated the effect of CN⁻.     

Nitric oxide is involved in salicylic acid-induced flowering of Lemna aequinoctialis Welw.

Salicylic acid (SA) is a well-known inducer of flowering in Lemna under both non-inductive and inductive photoperiod conditions. However, the underlying mechanism is not well understood. Herein, we report for the first time that nitric oxide (NO) is partially involved in SA-induced flowering in L. aequinoctialis (Syn. L. paucicostata Hegelm.). Our results demonstrated that SA-induced flowering is significantly reduced by exogenous application of NO scavengers; 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and methylene blue, nitric oxide synthase inhibitors; N-ω-nitro-l-arginine and N-ω-nitro-l-arginine-methyl ester hydrochloride, and nitrate reductase inhibitor; sodium tungstate in two strains of Lemna viz. 6746 and LP₆. Altogether our present findings shed a light on the new role of NO in SA-induced flowering and open interesting directions that need further investigation.     

DNA barcoding of endangered Indian Paphiopedilum species

The indiscriminate collections of Paphiopedilum species from the wild for their exotic ornamental flowers have rendered these plants endangered. Although the trade of these endangered species from the wild is strictly forbidden, it continues unabated in one or other forms that elude the current identification methods. DNA barcoding that offers identification of a species even if only a small fragment of the organism at any stage of development is available could be of great utility in scrutinizing the illegal trade of both endangered plant and animal species. Therefore, this study was undertaken to develop DNA barcodes of Indian species of Paphiopedilum along with their three natural hybrids using loci from both the chloroplast and nuclear genomes. The five loci tested for their potential as effective barcodes were RNA polymerase-β subunit (rpoB), RNA polymerase-β' subunit (rpoC1), Rubisco large subunit (rbcL) and maturase K (matK) from the chloroplast genome and nuclear ribosomal internal transcribed spacer (nrITS) from the nuclear genome. The intra- and inter-specific divergence values and species discrimination rates were calculated by Kimura 2 parameter (K2P) method using mega 4.0. The matK with 0.9% average inter-specific divergence value yielded 100% species resolution, thus could distinguish all the eight species of Paphiopedilum unequivocally. The species identification capability of these sequences was further confirmed as each of the matK sequences was found to be unique for the species when a blast analysis of these sequences was carried out on NCBI. nrITS, although had 4.4% average inter-specific divergence value, afforded only 50% species resolution. DNA barcodes of the three hybrids also reflected their parentage.