Tamoxifen and estrogens as membrane antioxidants: comparison with cholesterol

Complex interactions of lovastatin with 10 chemotherapeutic drugs: a rigorous evaluation of synergism and antagonism

Background

Evidence bearing on the role of statins in the prevention and treatment of cancer is confounded by the diversity of statins, chemotherapeutic agents and cancer types included in the numerous published studies; consequently, the adjunctive value of statins with chemotherapy remains uncertain.

Methods

We assayed lovastatin in combination with each of ten commonly prescribed chemotherapy drugs in highly reproducible in vitro assays, using a neutral cellular substrate, Saccharomyces cerevisiae. Cell density (OD₆₀₀) data were analyzed for synergism and antagonism using the Loewe additivity model implemented with the Combenefit software.

Results

Four of the ten chemotherapy drugs – tamoxifen, doxorubicin, methotrexate and rapamycin – exhibited net synergism with lovastatin. The remaining six agents (5-fluorouracil, gemcitabine, epothilone, cisplatin, cyclophosphamide and etoposide) compiled neutral or antagonistic scores. Distinctive patterns of synergism and antagonism, often coexisting within the same concentration space, were documented with the various combinations, including those with net synergism scores. Two drug pairs, lovastatin combined with tamoxifen or cisplatin, were also assayed in human cell lines as proof of principle.

Conclusions

The synergistic interactions of tamoxifen, doxorubicin, methotrexate and rapamycin with lovastatin – because they suggest the possibility of clinical utility - merit further exploration and validation in cell lines and animal models. No less importantly, strong antagonistic interactions between certain agents and lovastatin argue for a cautious, data-driven approach before adding a statin to any chemotherapeutic regimen. We also urge awareness of adventitious statin usage by patients entering cancer treatment protocols.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-07963-w.

Effects of ovarian sex hormones and downhill running on fiber-type-specific HSP70 expression in rat soleus

This study examined the influence of the ovarian sex hormones, estrogen and progesterone, on the fiber-type-specific response of the inducible 70-kDa heat shock protein (HSP70) to damaging exercise in rat soleus. Ovariectomized female rats were divided into three treatment groups (n = 16 per group): sham (S), progesterone (P; 25 mg pellet), and estrogen (E; 0.25 mg pellet). Each treatment group was divided into control and exercised groups. After 8 days of sham or hormone treatment, animals ran downhill intermittently for 90 min (17 m/min, -13.5 degrees grade) on a treadmill, and soleus muscles were removed 24 h postexercise. HSP70 expression was assessed in whole muscle homogenates by Western blotting and in individual muscle fiber types by immunohistochemical analysis of serial cross sections of soleus samples. Comparisons between control groups showed that HSP70 expression in soleus was increased (P < 0.05) in E compared with both S and P. No difference (P > 0.05) was observed between S and P. Following downhill running, HSP70 content in soleus was increased (P < 0.05) compared with control in S and P, but not (P > 0.05) in E. As a result, soleus HSP70 content following downhill running was not different (P > 0.05) between any of the treatment groups. Under all conditions, HSP70 content was higher in type I vs. type II fibers, and the effects of both estrogen and exercise on HSP70 expression in soleus were also more pronounced in type I vs. type II fibers. These results demonstrate that 1) estrogen regulates HSP70 expression in skeletal muscle, increasing basal HSP70 expression and preventing further increases in HSP70 in response to exercise; 2) progesterone is not involved in the regulation of HSP70 expression in skeletal muscle; and 3) the effects of estrogen and exercise on HSP70 expression in skeletal muscle are fiber type specific.

Heat shock proteins and exercise: a primer

Heat shock proteins (HSPs) are, in general, prosurvival molecules within the cellular environment, and the overexpression of even just 1 family of HSPs can lead to protection against and improvements after a variety of stressors. Not surprisingly, a fertile area of study has grown out of efforts to exploit the innate biologic behaviour of HSPs. Exercise, because of the inherent physiologic stresses associated with it, is but 1 stimulus that can result in a robust increase in various HSPs in several tissues, not the least of which happen to be the heart and skeletal muscle. The purpose of this review is to introduce the reader to the major HSP families, the control of their expression, and some of their biologic functions, specifically with respect to the influence of exercise. Moreover, as the first in a series of reviews from a common symposium, we will briefly introduce the concepts presented by the other authors, which include the effects of different exercise paradigms on skeletal muscle HSPs in the adult and aged systems, HSPs as regulators of inflammation, and the ion channel stabilizing effects of HSPs.

Therapeutic uses of antioxidant liposomes

This review will focus on the therapeutic uses of antioxidant liposomes. Antioxidant liposomes have a unique ability to deliver both lipid- and water-soluble antioxidants to tissues. This review will detail the varieties of antioxidants which have been incorporated into liposomes, their modes of administration, and the clinical conditions in which antioxidant liposomes could play an important therapeutic role. Antioxidant liposomes should be particularly useful for treating diseases or conditions in which oxidative stress plays a significant pathophysiological role because this technology has been shown to suppress oxidative stress. These diseases and conditions include cancer, trauma, irradiation, retinotherapy or prematurity, respiratory distress syndrome, chemical weapon exposure, and pulmonary infections.

Ethanolamine plasmalogen and cholesterol reduce the total membrane oxidizability measured by the oxygen uptake method

To investigate the effects of ethanolamine plasmalogen, phosphatidylethanolamine, cholesterol, and alpha-tocopherol on the oxidizability of membranes, various large unilamellar vesicles (LUVs) including these lipids and antioxidant were examined for their total membrane oxidizabilities, evaluated as R(p)/R(i)(1/2) value (where R(p) is rate of oxygen consumption and R(i)(1/2) is the square root of rate of chain initiation) by the oxygen uptake method with water-soluble radical initiator and inhibitor. Incorporation of bovine brain ethanolamine plasmalogen (BBEP) into vesicles as well as cholesterol led to lower the total membrane oxidizability dose-dependently. The effect of BBEP was more efficient in the presence of cholesterol in vesicles. On the other hand, diacyl counterpart, egg yolk phosphatidylethanolamine, and a typical radical scavenger, alpha-tocopherol, had no effect on the membrane oxidizability. Alpha-tocopherol only prolonged an induction period dose-dependently in the present oxidizing system, suggesting a novel antioxidant mechanism of ethanolamine plasmalogens besides the action of scavenging radicals.

Therapeutic uses of antioxidant liposomes

This chapter focuses on the use of antioxidant liposomes in the general area of free radical biology and medicine. The term antioxidant liposome is relatively new and refers to liposomes containing lipid-soluble chemical antioxidants, water-soluble chemical antioxidants, enzymatic antioxidants, or combinations of these various antioxidants. The role of antioxidants in health and disease has been extensively discussed, and many excellent reviews and books are available (1–3). Antioxidant liposomes hold great promise in the treatment of many diseases in which oxidative stress plays a prominent role. Oxidative stress is a physiological condition in which the production of damaging free radicals exceeds the in vivo capacity of antioxidant protection mechanisms to prevent pathophysiology. Free radicals are molecules with unpaired electrons, often highly reactive and damaging to biological systems. The biological membranes of subcellular organelles are a major site of free radical damage but proteins and DNA are also significant targets. Moreover, free radicals can alter cellular signal transduction pathways and stimulate the synthesis of inflammatory cytokines. Oxygen radicals and other reactive oxygen species (ROS) arise from the single electron reductions of oxygen.

Antioxidant effect of estrogen on cytomegalovirus-induced gene expression in coronary artery smooth muscle cells

BACKGROUND

Pathogens infecting the arterial wall with resultant inflammation may contribute to atherogenesis. Human coronary artery smooth muscle cells (SMCs) infected with human cytomegalovirus (CMV) demonstrate a rapid increase in reactive oxygen species (ROSs), with activation of genes involved in viral replication and inflammation. Because estrogen appears to have antioxidant properties, we wished to determine whether this hormone attenuates SMC responses to CMV infection.

METHODS AND RESULTS

Using confocal microscopy and an intracellular fluorescent dye activated by ROSs, we found that 17beta-estradiol (0.1 to 10 nmol/L) and its stereoisomer 17alpha-estradiol (which has low affinity for the estrogen receptor) dose-dependently inhibited ROS generation in CMV-infected SMCs. These effects were not blocked by the estrogen receptor inhibitor ICI 182,780. 3-Methoxyestrone, which lacks the phenolic hydroxyl group, did not interfere with ROS generation. We found that 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, prevented binding of nuclear factor (NF)-kappaB to DNA. Furthermore, in SMCs transfected with the reporter constructs 3XkappaB-CAT, MIEP-CAT, or ICAM-CAT, cotransfection with a CMV-IE72 expression plasmid caused promoter and CAT activation. Treatment with 17beta-estradiol and 17alpha-estradiol, but not 3-methoxyestrone, inhibited CAT activity and, in CMV-infected SMCs, prevented IE72 and ICAM-1 protein expression and cytopathic effects.

CONCLUSIONS

These findings indicate that estrogen molecules with an A-ring hydroxyl group have estrogen receptor-independent anti-CMV effects at physiological concentrations by inhibiting ROS generation, NF-kappaB activation, NF-kappaB-dependent transcription, and viral replication. To the extent that chronic infection of the vascular wall with CMV contributes to atherogenesis, these antioxidant actions of estrogen may be of therapeutic importance.

Modulation of liposomal membrane fluidity by flavonoids and isoflavonoids

The polyphenolic structures of flavonoids and isoflavonoids confer them with the ability to scavenge free radicals and to chelate transition metals, a basis for their potent antioxidant abilities. Another possible contributory mechanism toward their antioxidant activities is their ability to stabilize membranes by decreasing membrane fluidity. In this study, the effects of representative flavonoids, isoflavonoids, and their metabolites on membrane fluidity and their preferential localization in the membrane were investigated using large unilamellar vesicles (LUVs) as the membrane models. These results were compared with those of cholesterol and alpha-tocopherol. Changes in fluorescence anisotropy values for a series of n-(9-anthroyloxy) fatty acid probes (n = 6, 12, 16) upon addition of the test compounds were used to monitor alterations in membrane fluidity at graded depths in lipid bilayer. The results of the study suggest that the flavonoids and isoflavonoids, similar to cholesterol and alpha-tocopherol, partition into the hydrophobic core of the membrane and cause a dramatic decrease in lipid fluidity in this region of the membrane. Localization of flavonoids and isoflavonoids into the membrane interiors and their resulting restrictions on fluidity of membrane components could sterically hinder diffusion of free radicals and thereby decrease the kinetics of free radical reactions.

Review of progress in sterol oxidations: 1987-1995

Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.