A new method for delivering alkanes to mammalian cells: preparation and preliminary characterization of an inclusion complex between beta-cyclodextrin and pristane (2,6,10,14-tetramethylpentadecane)

Pristane (2,6,10,14-tetramethylpentadecane) is an isoalkane which induces plasma cell tumorigenesis in genetically susceptible strains of mice. Attempts to study the biological activity of pristane on cells in vitro have been hindered by the extreme hydrophobicity and hence complete immiscibility of the compound in aqueous cell culture media. In comparing different solubilization protocols such as using organic solvents, liposomes, and molecular encapsulation into beta-cyclodextrin (beta-CyD), it was found that beta-CyD/pristane inclusion complexes were optimal for delivery of the hydrocarbon to cells. After solubilization in beta-CyD, pristane was cytotoxic (51Cr release assay) to murine B lymphocyte lines in culture (P388, NSF-1, and SJL-4) and inhibited the lipopolysaccharide-induced stimulation of splenic B lymphocyte proliferation and blast formation (Coulter counter analysis) when added in the micromolar concentration range. Moreover, sub-toxic concentrations of beta-CyD/pristane inclusion complexes were found to have a small but reproducible mitogenic effect [( 3H]thymidine incorporation) on SJL-4 and 308 (murine initiated keratinocyte) cells in culture but not on P388 cells. The results indicate that molecular encapsulation of pristane into beta-CyD provides a new and effective method for delivering low concentrations of alkanes to mammalian cells in vitro.     

Chronic inflammation and cancer: the role of the mitochondria

Accumulating evidence shows that chronic inflammation can promote all stages of tumorigenesis, including DNA damage, limitless replication, apoptosis evasion, sustained angiogenesis, self-sufficiency in growth signaling, insensitivity to anti-growth signaling, and tissue invasion/metastasis. Chronic inflammation is triggered by environmental (extrinsic) factors (eg, infection, tobacco, asbestos) and host mutations (intrinsic) factors (eg, Ras, Myc, p53). Extensive investigations over the past decade have uncovered many of the important mechanistic pathways underlying cancer-related inflammation. However, the precise molecular mechanisms involved and the interconnecting crosstalk between pathways remain incompletely understood. We review the evidence implicating a strong association between chronic inflammation and cancer, with an emphasis on colorectal and lung cancer. We summarize the current knowledge of the important molecular and cellular pathways linking chronic inflammation to tumorigenesis. Specifically, we focus on the role of the mitochondria in coordinating life- and death-signaling pathways crucial in cancer-related inflammation. Activation of Ras, Myc, and p53 cause mitochondrial dysfunction, resulting in mitochondrial reactive oxygen species (ROS) production and downstream signaling (eg, NFkappaB, STAT3, etc.) that promote inflammation-associated cancer. A recent murine transgenic study established that mitochondrial metabolism and ROS production are necessary for K-Ras-induced tumorigenicity. Collectively, inflammation-associated cancers resulting from signaling pathways coordinated at the mitochondrial level are being identified that may prove useful for developing innovative strategies for both cancer prevention and cancer treatment.     

Treatment of scabies and pediculosis with lindane preparations: an evaluation

Risks and benefits involved in the use of lindane preparations for the treatment of scabies and head louse infestations are evaluated. Although lindane per si is moderately toxic, capable of inducing neurotoxic and hemotoxic effects, there is little evidence that the preparations used in the treatment of scabies and pediculosis give rise to toxic symptoms when applied according to directions. Current evidence does not support the view that lindane is intrinsically carcinogenic, although very high doses have induced hepatomas in mice. It is concluded that the benefits obtained in the use of lindane as a scabicide and pediculicide outweigh risks involved in its use for these purposes. Comparison with other preparations available for the control of scabies and pediculosis indicate that lindane is probably the most effective scabicide, although it also shows the greatest toxic potential. Malathion and pyrethrin preparations seem equally effective against head lice. Suggestions for even safer use of lindane are discussed.     

Rho GDP dissociation inhibitor protects cancer cells against drug-induced apoptosis

Rho GDP dissociation inhibitor (RhoGDI) plays an essential role in control of a variety of cellular functions through interactions with Rho family GTPases, including Rac1, Cdc42, and RhoA. RhoGDI is frequently overexpressed in human tumors and chemo-resistant cancer cell lines, raising the possibility that RhoGDI might play a role in the development of drug resistance in cancer cells. We found that overexpression of RhoGDI increased resistance of cancer cells (MDA-MB-231 human breast cancer cells and JLP-119 lymphoma cells) to the induction of apoptosis by two chemotherapeutic agents: etoposide and doxorubicin. Conversely, silencing of RhoGDI expression by DNA vector-mediated RNA interference (small interfering RNA) sensitized MDA-MB-231 cells to drug-induced apoptosis. Resistance to apoptosis was restored by reintroduction of RhoGDI protein expression. The mechanism for the anti-apoptotic activity of RhoGDI may derive from its ability to inhibit caspase-mediated cleavage of Rac1 GTPase, which is required for maximal apoptosis to occur in response to cytotoxic drugs. Taken together, the data show that RhoGDI is an anti-apoptotic molecule that mediates cellular resistance to these chemotherapy agents.     

The iron chelator Dp44mT inhibits the proliferation of cancer cells but fails to protect from doxorubicin-induced cardiotoxicity in spontaneously hypertensive rats

Purpose  

The iron chelator Dp44mT is a potent topoisomerase IIα inhibitor with novel anticancer activity. Doxorubicin (Dox), the current front-line therapy for breast cancer, induces a dose-limiting cardiotoxicity, in part through an iron-mediated pathway. We tested the hypothesis that Dp44mT can improve clinical outcomes of treatment with Dox by alleviating cardiotoxicity.     

Ascorbate in pharmacologic concentrations selectively generates ascorbate radical and hydrogen peroxide in extracellular fluid in vivo

Ascorbate (ascorbic acid, vitamin C), in pharmacologic concentrations easily achieved in humans by i.v. administration, selectively kills some cancer cells but not normal cells. We proposed that pharmacologic ascorbate is a prodrug for preferential steady-state formation of ascorbate radical (Asc(*-)) and H(2)O(2) in the extracellular space compared with blood. Here we test this hypothesis in vivo. Rats were administered parenteral (i.v. or i.p.) or oral ascorbate in typical human pharmacologic doses ( approximately 0.25-0.5 mg per gram of body weight). After i.v. injection, ascorbate baseline concentrations of 50-100 microM in blood and extracellular fluid increased to peaks of >8 mM. After i.p. injection, peaks approached 3 mM in both fluids. By gavage, the same doses produced ascorbate concentrations of <150 microM in both fluids. In blood, Asc(*-) concentrations measured by EPR were undetectable with oral administration and always <50 nM with parenteral administration, even when corresponding ascorbate concentrations were >8 mM. After parenteral dosing, Asc(*-) concentrations in extracellular fluid were 4- to 12-fold higher than those in blood, were as high as 250 nM, and were a function of ascorbate concentrations. By using the synthesized probe peroxyxanthone, H(2)O(2) in extracellular fluid was detected only after parenteral administration of ascorbate and when Asc(*-) concentrations in extracellular fluid exceeded 100 nM. The data show that pharmacologic ascorbate is a prodrug for preferential steady-state formation of Asc(*-) and H(2)O(2) in the extracellular space but not blood. These data provide a foundation for pursuing pharmacologic ascorbate as a prooxidant therapeutic agent in cancer and infections.     

Hypercalcemia during the osteogenic phase after rat marrow ablation coincides with increased bone resorption assessed by the NTx marker

Marrow ablation is a model of bone turnover in which the excavated tibial intramedullary cavity is rapidly and reproducibly filled by osteoblasts with new woven bone (days 6-8), which is then rapidly resorbed by osteoclasts (days 10-15). We showed previously (Magnuson et al., 1997) that marrow ablation induces a dramatic hypercalcemia and hypercalciuria in rats that unexpectedly peaked at the time of maximal osteogenesis and continued throughout the subsequent resorption phase. Based upon the amount of calcium mobilized and a peak of urinary hydroxyproline, we suggested that the hypercalcemia and hypercalciuria were due to increased systemic osteoclastic bone resorption induced by marrow ablation. We now apply a new enzyme-linked immunosorbent assay for rodent alpha(2)(I) N-telopeptide (NTx), a marker of bone resorption, to the marrow ablation model to demonstrate that excretion of NTx parallels that of calcium release in the operated control group. Specifically, maximal NTx/creatinine excretion coincides with the onset of hypercalcemia on days 7-8. A peak of NTx was also observed in methylprednisolone- and deflazacort-treated ablated animals. Analyses for urinary free deoxypyridinoline crosslink failed to detect a significant ablation-induced change in excretion. Interleukin 6 activity was increased in all operated control and glucocorticoid-treated groups after marrow ablation, whereas serum parathyroid hormone remained at presurgical levels in operated controls throughout the 15-day study period. The NTx results confirm that bilateral tibial marrow ablation induces a burst of extratibial bone resorption and hypercalcemia 7-8 days later. We have estimated that the osteogenic phase of the ablation model deposits 40 mg of calcium as hydroxyapatite crystals within the intramedullary cavity on days 6-8; this represents 33%-50% of the total blood calcium content of a young rat. We hypothesize that the size and rapidity of this demand for ionized calcium is met through an extratibial bone resorption pathway of osteoclast formation and activation that anticipates and fulfills this need, and that is initiated at the time of marrow ablation.     

Serum-derived protein S binds to phosphatidylserine and stimulates the phagocytosis of apoptotic cells

Rapid phagocytosis of apoptotic cells is thought to limit the development of inflammation and autoimmune disease. Serum enhances macrophage phagocytosis of apoptotic cells. Here we identified protein S as the factor responsible for serum-stimulated phagocytosis of apoptotic cells. Protein S is best known for its anti-thrombotic activity, serving as a cofactor for protein C. Purified protein S was equivalent to serum in its ability to stimulate macrophage phagocytosis of apoptotic lymphoma cells, and immunodepletion of protein S eliminated the prophagocytic activity of serum. Protein S acted by binding to phosphatidylserine expressed on the apoptotic cell surface. Protein S is thus a multifunctional protein that can facilitate clearance of early apoptotic cells in addition to regulating blood coagulation.