Potentiation of tumor necrosis factor-mediated cytotoxicity on human myeloid cell lines: effects of interferons versus dimethylsulphoxide

Adherent cell assay results affected by variable z-position mixing

We demonstrate that modifying mixing dynamics after addition of organic solute into aqueous buffers dramatically affects cell morphology and protein expression. Variable z-position (VZP) or varying the height of aspiration and dispense positions during mixing eliminates artifactual effects. Here, we tested 4 adherent cell types and show effects of VZP on quantitative imaging, protein expression, viability, and morphology. The result: The quantitation of cytoplasmic fluorescence within the fields of interest of the phalloidin-actin stain assay improved by 47% and fluorescence variability emitted by cells expressing green fluorescence protein (GFP) fusion proteins decreased by 15%. Assays that perform measurement by averaged reading of the entire well are somewhat susceptible. For example, protein production decreased 8% on the hypoxia response element (HRE)-luciferase assay. VZP did not affect quantitative cell viability, deviate the half maximal effective dose concentration (EC(50)) values or alter expected curve patterns. VZP is a valuable systematic process for cellular assay workflows as it efficiently folds organic solute into the aqueous solution.

Endogenous carriers and ligands in non-immunogenic site-specific drug delivery

Targeted drug delivery has gained recognition in modern therapeutics and attempts are being made to explore the potentials and possibilities of cell biology related bioevents in the development of specific, programmed and target oriented systems. The components which have been recognized to be tools include receptors and ligands, where the receptors act as molecular targets or portals, and ligands, with receptor specificity and selectivity, are trafficked en route to the target site. Although ligands of exogenous or synthetic origin contribute to the selectivity component of carrier constructs, they may impose immunological manifestations of different magnitudes. The latter may entail a continual quest for bio-compatible, non-immunogenic and target orientated delivery. Endogenous serum, cellular and extracellular bio-ligands interact with the colloidal carrier constructs and influence their bio-fate. However, these endogenous bio-ligands can themselves serve as targeting modules either in their native form or engineered as carrier cargo. Bio-regulatory, nutrient and immune ligands are sensitive, specific and effective site directing handles which add to targeted drug delivery. The present review provides an exhaustive account of the identified bio-ligands, which are not only non-immunogenic in nature but also site-specific. The cell-related bioevents which are instrumental in negotiating the uptake of bio-ligands are discussed. Further, a brief account of ligand-receptor interactions and the set of biological events which ensures ligand-driven trafficking of the ligand-receptor complex to the cellular interior is also presented. Since ligand-receptor interaction is a critical pre-requisite for negotiating cellular uptake of endogenous ligands and anchored carrier cargo, an attempt has been made to identify differential expression of receptors and bio-ligands under normal and etiological conditions. Studies which judiciously utilized bio-ligands or their analogs in negotiating site-specific drug delivery have been reviewed and presented. Targeted delivery of bioactives using endogenous bio-ligands offers enormous options and opportunities through carrier construct engineering and could become a future reality in clinical practice.

Inhibition of calmodulin-stimulated (Ca2+ + Mg2+)-ATPase activity by dimethyl sulfoxide

Membrane-bound (Ca2+ + Mg2+)-ATPase activity from human erythrocyte white ghosts in the calmodulin-activated state was inhibited by DMSO in concentrations of 3% (v/v) and above. At 10%, DMSO inhibited calmodulin activation by 47.7%, while basal, calmodulin-independent (Ca2+ + Mg2+)-ATPase and (Mg2+)-ATPase activity remained unaffected. (Na+ + K+)-ATPase activity was also reduced but exhibited a greater IC50. Concentration-effect analyses showed the inhibition by 10% DMSO to be a reversible, non-competitive effect with regard to calmodulin, Ca2+, and substrate activation. Calmodulin-stimulated processes may be more susceptible to inhibition by DMSO than related enzymatic catalysis, and thus may help explain the multitude of reported cellular events caused by the solvent. Furthermore, DMSO affected membrane-associated enzymatic mechanisms opposite to those reported for purified enzyme outside its native membrane environment.

The influence of recombinant human tumor necrosis factor alpha and its muteins used alone or in combination with 2-chlorodeoxyadenosine on normal and leukemic hematopoiesis in vitro

We investigated the influence of TNF alpha and its muteins III, V and VI on the colony growth of normal and CML CFU-GM cells as well as on CFU-L clonogenic blasts from AML patients in cultures in vitro. The muteins were constructed using a synthetic cDNA fragment substituting nucleotides coding for the N-terminal amino acids in the chain of native TNF alpha. We observed that TNF alpha and mutein VI inhibited the growth of colonies formed by both types of CFU-GM and CFU-L cells in a greater degree than muteins III and V. In addition, the percentage of colony growth inhibition after the use of mutein VI was the greatest. These observations were the basis for the evaluation of interaction between 2-CdA and TNF alpha and between 2-CdA and mutein VI. We have confirmed that 2-CdA used together with mutein VI acts synergistically on CFU-GM and CFU-L cells, whereas 2-CdA and TNF alpha show the additive effect.

Differentiation of human trophoblast cells in vitro is inhibited by dimethylsulfoxide

Dimethyl sulfoxide (DMSO) exerts a number of biological effects, the most frequently cited being induction of cell differentiation. The compound also increases invasiveness and metastatic potential. In contrast to the many reports of DMSO-induced cell differentiation, we report here that DMSO inhibits the morphological differentiation of human cytotrophoblast cells to syncytiotrophoblast, as revealed by immunofluorescence staining for desmosomal protein and nuclei. Cytotrophoblast cells treated with DMSO under differentiation-inducing conditions remained mononucleated with intense desmosomals staining. The effect was dose dependent, with a maximal effect seen at 1.5% DMSO. Concentrations of < or = 0.5% had no effect and concentrations > 2% were cytotoxic. In addition to these morphological changes, DMSO inhibited secretion of human chorionic gonadotropin in a dose-dependent manner. At a concentration of 1.5%, DMSO inhibited secretion by 70%. If cytotrophoblast cells were cultured in the presence of DMSO and then switched to DMSO-free medium, they proceeded to differentiate normally. While the precise mechanism of action remains unknown, judicious use of DMSO may be a useful tool for studying and manipulating the differentiation of human trophoblast cells in vitro. The findings also indicate that care should be used in interpreting results obtained using DMSO as a carrier in drug and inhibitor studies.