Effects of doxorubicin, 4'-epirubicin, and antioxidant enzymes on the contractility of isolated cardiomyocytes

The purpose of this study was to determine the acute effects of doxorubicin and its less cardiotoxic epimer, 4'-epirubicin, on the contractile response of isolated myocytes, and to assess similarities or differences with respect to active oxygen-derived mechanisms. Calcium-tolerant myocytes from rat ventricle were field stimulated at 1.0 Hz, and the maximum extent of cell shortening, peak shortening velocity, and peak relaxation velocity of single twitches were measured by video edge detection. The contractile responses of the myocytes to the two anthracyclines were approximately equal. Exposure of the cells to 10 microM of either anthracycline for 20 min decreased all indices of contractility by 28% (p < 0.05). The active oxygen scavengers, superoxide dismutase and catalase, distinguished the extent to which active oxygen was involved in modifying cellular contractility. Paradoxically, superoxide dismutase alone (10 U/mL) decreased contractility by 21%. Nevertheless, superoxide dismutase (10 U/mL) prevented the decreases in contractility produced by doxorubicin. In contrast, superoxide dismutase only mildly (32%) protected against 4'-epirubicin. Catalase (10 U/mL), however, provided substantial (82-93%) protection against both anthracyclines. Hydrogen peroxide therefore, and presumably hydroxyl radicals, were involved in mediating the decreases in contractility from both doxorubicin and 4'-epirubicin. These results show that an acute exposure to clinically relevant concentrations of these anthracyclines significantly depresses myocyte contractility and that, in this respect, 4'-epirubicin is as potentially cardiotoxic as doxorubicin. The results with antioxidant enzymes also strongly support a free radical mechanism for the toxicity of doxorubicin and 4'-epirubicin to cardiomyocytes.

Consensus conference on autologous transfusion. Acute normovolaemic haemodilution

ANH is a relatively cheap and logistically straightforward method of autologous transfusion which is attractive in that it may be applied to a wide cross-section of patients, many of whom will not be suitable for pre-deposit. There are, however, concerns about the safety of the procedure, and doubts have been expressed about its efficacy in reducing allogeneic transfusion requirements and, therefore, its cost-effectiveness. Assessment of the value of the procedure is hampered by the lack of large scale prospective, controlled trials. In the present state of knowledge it seems that ANH is most likely to be safe, efficacious and cost-effective when undertaken aggressively (target haematocrit < 0.20) in otherwise healthy, young patients undergoing elective surgery with large expected blood losses.

Noninvasive and minimally invasive carcinoma ex mixed tumor: a clinicopathologic and ploidy study of 12 patients with major salivary tumors of low (or no?) malignant potential

We studied 12 histologically malignant salivary tumors that showed complete encapsulation or only limited microscopic invasion. Most cases were histologically characterized by atypical and mitotically active luminal cells forming dilated, angular, variably sized glands in the subcapsular region, varying proportions of nonluminal tumor cells, and a background of central fibrosed hyalinized stroma. The appearance is that of a low-grade carcinoma. Focal higher grade carcinoma was superimposed on this histologic data in three cases. Neither recurrences nor metastases were seen in 11 of 12 patients after surgical resection with a follow-up of 1.2 to 13 yrs (mean, 4.2 years). Ploidy studies were performed on the paraffin-embedded tissue in 11 cases and yielded results for 7 cases. Aneuploid cell populations were found in five tumors; two had normal diploid populations; and the ploidy results are not predictive of tumor behavior. This type of salivary gland tumor fits diagnostically within the category of noninvasive and minimally invasive carcinoma ex pleomorphic adenoma (also referred to as in situ and low-grade malignant mixed tumors), a class that requires additional awareness and precise recognition as it signifies a good prognosis after surgical resection.

Dietary fatty acids, low density lipoprotein composition and oxidation and primate atherosclerosis

Low density lipoproteins (LDL) were isolated from nonhuman primates fed isocaloric diets rich in different types of fatty acids. These diets contained 35% of calories as fat enriched in fatty acids from the following sources: lard that is rich in saturated fatty acids, safflower oil rich in oleic acid, safflower oil rich in linoleic acid and menhaden oil that is rich in n-3 fatty acids. LDL composition reflected the dietary fats. LDL were subjected to oxidation using copper ions and azobis(2-amidinopropane) x 2HCl. In general, the sensitivity of LDL to oxidation depended on both the poly-unsaturated fatty acid and vitamin E content. However, the lag times calculated for the copper ion catalyzed oxidations did not show the linear dependence on vitamin E content that was found for azobis(2-amidinopropane) catalyzed oxidation.

High level secretion of wild-type and mutant forms of human proapoA-I using baculovirus-mediated Sf-9 cell expression

To facilitate the investigation of apoA-I structure:function relationships as they relate to LCAT activation and lipid binding, we have developed an apoA-I baculoviral expression and purification system that yields milligram quantities of wild-type or mutant proapoA-I. Baculovirus-infected Sf-9 cells, grown in suspension, were found to secrete high levels of human wild-type (40-50 mg/l) or mutant apoA-I protein (1-38 mg/l), which was determined to be > 95% pure following a two-step purification procedure. In the case of wild-type apoA-I, ELISA showed that approximately 13-18% of the total protein secreted into the culture medium was apoA-I. To isolate pure protein from culture medium, 72 h post-infection medium was subjected to preparative reverse phase high performance liquid chromatography (HPLC), followed by DEAE ion-exchange chromatography. Purity and molecular size determination of wild-type proapoA-I protein was verified by SDS polyacrylamide gel electrophoresis, electrospray mass spectrometry, and N-terminal sequencing. In addition, recombinant discoidal apoA-I:phospholipid complexes prepared from wild-type or plasma apoA-I showed similar particle size and LCAT activation properties. To fully characterize the utility of this expression system, the expression levels of various mutant apoA-I proteins were compared to wild-type. Despite a lower production level seen with selected apoA-I mutants, milligram quantities of these purified mutant proteins were also obtained. In summary, we show that baculovirus-derived wild-type proapoA-I shows properties similar to plasma apoA-I relative to recombinant HDL formation, LCAT reactivity, and alpha-helical content. In addition, we show that a variety of mutant forms of human proapoA-I can be expressed and purified in abundant quantity from baculoviral-infected Sf-9 cells.

Products of ozonized arachidonic acid potentiate the formation of DNA single strand breaks in cultured human lung cells

In this study we examined the potential for environmental levels of ozone (03) to degrade arachidonic acid (AA), a polyunsaturated fatty acid abundantly present in the lung, into products that can produce DNA single strand breaks (ssb) in cultured human lung cells. Human lung fibroblasts were incubated with 60 microM AA that had been previously exposed to and degraded by 0.4 ppm 03 (1 hr.) Incubation of the cells with 03-exposed AA (but not with vehicle alone) for 1 hr at 4 degrees C and 37 degrees C produced 555 and 245 rad-equivalents of DNA ssb, respectively, as determined by the DNA alkaline elution technique. These breaks were completely eliminated when the ozonized AA solution was incubated with catalase prior to cell treatment, indicating that h202 was solely responsible for damaging DNA. Superoxide dismutase bovine serum albumin, or heat-inactivated catalase showed little, if any, inhibitory activity. The H202 content of the ozonized AA (31 +/- 4 microM) could account for only about 40% of the observed breaks. Potentiation of the H202-induced DNA ssb persisted after removal of the carbonyl substances by chromatographic procedures, suggesting that the non-carbonyl component of ozonized AA was the responsible component for inducing augmentation of the observed increases in DNA ssb. Ozonized AA also induced DNA ssb in cultures of the human bronchial epithelial cell line BEAS-2B. Again, these breaks were shown to exceed levels that could be attributed to the presence of H202 alone. These results indicate that products of ozonized AA can interact to potentiate DNA ssb in human lung cells.

The use of rheumatoid factors in clinical practice

Rheumatoid factor is a commonly requested test in the investigation of joint problems. Although the test has been found to be both sensitive and specific for rheumatoid arthritis in patients attending Rheumatology Clinics, when the test is applied to general hospital or community populations it performs poorly. Thus the setting in which rheumatoid factor tests are requested and awareness of the test's limitations are critical for appropriate use and interpretation of results. We studied 295 consecutive requests for testing at four centres. The majority were performed for the investigation of joint problems but only 6% of these were positive, suggesting unselective requesting. Half of the results were used to make diagnoses and influence management. However, significant numbers of clinicians felt that the test result had either excluded or confirmed a diagnosis of rheumatoid arthritis suggesting that results were being over-interpreted and that clinical decisions made on this basis may have been inappropriate. We conclude that in this setting rheumatoid factor testing is of limited value and generates misleading information.

The molecular switch hypothesis fails to explain the inconsistent effects of the metabotropic glutamate receptor antagonist MCPG on long-term potentiation

In the CA1 region of the hippocampus, the induction of long-term potentiation (LTP) appears to be controlled by a switch-like biochemical process that is persistently activated following metabotropic glutamate receptor (mGLUR) activation. However, the mGLUR antagonist (RS)-alpha-methyl-4-carboxyphenylglycine (MCPG) does not consistently block the induction of LTP, perhaps because the experimental conditions used by some investigators inadvertently activate this 'molecular switch', thereby fulfilling the requirement for mGLUR activation and rendering LTP insensitive to the effects of mGLUR antagonists. In mouse hippocampal slices we observed that MCPG does not block LTP induced by high-frequency stimulation, Moreover, stimulation protocols designed to deactivate an inadvertently activated molecular switch had no effect on the inability of MCPG to block LTP. MCPG (through a switch-independent mechanism) did inhibit the induction of LTP by a weak induction protocol. Our results thus suggest that MCPT-sensitive mGLURs are not required for the induction of LTP and that a mLGUR-activated 'molecular switch' does not explain the inconsistent effects of MCPG on LTP. Instead, MCPG-sensitive mGLURs may have a modulatory role in the induction of LTP that is most evident when LTP is induced by near threshold patterns of synaptic stimulation.

Hippocampal long-term potentiation is normal in heme oxygenase-2 mutant mice

We have generated mice deficient in HO-2, the major cerebral isoform of heme oxygenase, in order to assess the potential role of carbon monoxide as a retrograde messenger in hippocampal LTP. Cerebral HO catalytic activity was markedly reduced in the HO-2 mutant mice, yet no differences were found between wild types and mutants in gross neuroanatomical structure, in basal hippocampal synaptic transmission, or in the amount of potentiation produced by various LTP induction protocols. Furthermore, zinc protoporphyrin IX, an inhibitor of HO, had nearly identical inhibitory effects on LTP in wild-type and HO-2 mutant hippocampal slices. Our data indicate that carbon monoxide produced endogenously by HO is unlikely to be a neuromodulator required for LTP in the hippocampus.

Regulation of insulin-like growth factor I transcription by cyclic adenosine 3',5'-monophosphate (cAMP) in fetal rat bone cells through an element within exon 1: protein kinase A-dependent control without a consensus AMP response element

Insulin-like growth factor I (IGF-I) is a locally synthesized anabolic growth factor for bone. IGF-I synthesis by primary fetal rat osteoblasts (Ob) is stimulated by agents that increase the intracellular cAMP concentration, including prostaglandin E2 (PGE2). Previous studies with Ob cultures demonstrated that PGE2 enhanced IGF-I transcription through selective use of IGF-I promoter 1, with little effect on IGF-I messenger RNA half-life. Transient transfection of Ob cultures with an array of promoter 1-luciferase reporter fusion constructs has now allowed localization of a potential cis-acting promoter element(s) responsible for cAMP-stimulated gene expression to the 5'-untranslated region (5'-UTR) of IGF-I exon 1, within a segment lacking a consensus cAMP response element. Our evidence derives from three principal observations: 1) a transfection construct containing only 122 nucleotides (nt) of promoter 1 and 328 nt of the 5'-UTR retained full PGE2-stimulated reporter expression; 2) maximal PGE2-driven reporter expression required the presence of nt 196 to 328 of exon 1 when tested within the context of IGF-I promoter 1; 3) cotransfection of IGF-I promoter-luciferase-reporter constructs with a plasmid encoding the alpha-isoform of the catalytic subunit of murine cAMP-dependent protein kinase (PKA) produced results comparable to those seen with PGE2 treatment, whereas cotransfection with a plasmid encoding a mutant regulatory subunit of PKA that cannot bind cAMP blocked PGE2-induced reporter expression. Deoxyribonuclease I footprinting of the 5'-UTR of exon 1 demonstrated protected sequences at HS3A, HS3B, and HS3D, three of six DNA-protein binding sites previously characterized with rat liver nuclear extracts. Of these three regions, only the HS3D binding site is located within the functionally identified hormonally responsive segment of IGF-I exon 1. These results directly implicate PKA in the control of IGF-I gene transcription by PGE2 and identify a segment of IGF-I exon 1 as being essential for this hormonal regulation.

Fatty acids and plasma antioxidants in HIV-positive patients: correlation with nutritional and immunological status

OBJECTIVE

To investigate red blood cell (RBC) and plasma fatty acids (FA) in HIV-positive patients in relation to oxidative stress and nutritional or immunological status.

DESIGN AND METHODS

FA, plasma selenium, vitamins A and E were measured in 95 patients divided into four groups according to CD4 cells.

RESULTS

Poly- and di-unsaturated FA (PUFA, DUFA) decreased and saturated FA (SFA) increased in RBC in the patients below 400/mm3 and in plasma in the patients below 50/mm3. RBC SFA correlated to CD4 cells, PUFA to MDA. Unlike vitamin E, plasma vitamin A and selenium decreased in most groups. Plasma SFA and MUFA correlated negatively to selenium and PUFA and DUFA to vitamin E. No correlation was found between PUFA and nutritional markers.

CONCLUSION

FA seem to be modified during HIV infection by oxidative stress and disease evolution, but not by denutrition.

Release of aldehydes from rat alveolar macrophages exposed in vitro to low concentrations of nitrogen dioxide

This study demonstrated that aldehydes are released into the extracellular medium when alveolar macrophages (AM) are exposed to nitrogen dioxide (NO2) at concentrations that impair cell function but do not cause cell death. Butanal, glycolaldehyde, 4-hydroxynonenal, pentanal, pentenal, and hexanal were found. Dinitrophenylhydrazine (DNP) derivitization, thin layer chromatography, high performance liquid chromatography, and gas chromatography-mass spectrometry were used to identify the products. Some of the aldehydes have potential toxicity and may be responsible, in part, for altered AM function observed following NO2 exposure.

Rapid activation of rat insulin-like growth factor-I gene transcription by growth hormone reveals no changes in deoxyribonucleic acid-protein interactions within the second promoter

Insulin-like growth factor-I (IGF-I) is a highly conserved 70-residue circulating peptide that mediates many of the systemic growth-promoting effects of GH. This laboratory has found previously that GH rapidly stimulates hepatic IGF-I transcription in hypophysectomized (hypox) rats by activating promoter 1, the major rat IGF-I gene promoter. In this study, the hormonal regulation of IGF-I expression through promoter 2, a minor promoter in most tissues but active in the liver, was investigated. Through use of a sensitive RNase protection assay, GH was shown to rapidly induce the accumulation of correctly initiated transcripts directed by this promoter in hepatic nuclei. Using in vitro DNase-I footprinting, six DNA-protein interactions were identified within promoter 2 with hepatic nuclear extracts from juvenile male hypox rats given a single ip injection of GH or saline 60 min before death. These DNA-protein-binding complexes also were investigated for specificity and for regulation by GH by gel mobility shift assays. All DNA-protein interactions were detected in hepatic nuclear protein extracts from hypox rats and did not change within 15-120 min after GH treatment. These results thus identify and characterize a series of constitutive nuclear protein-binding sites within the second rat IGF-I promoter that may be involved in mediating its transcriptional activity.

Detecting and identifying volatile aldehydes as dinitrophenylhydrazones using gas chromatography mass spectrometry

The detection of aldehydes has become an important measure of lipid oxidation in biological milieu. Aldehyde 2,4-dinitrophenylhydrazones are easily prepared and readily purified by HPLC and/or TLC and have proven useful for the detection of aldehydes. The lower limit of detection for dinitrophenylhydrazones was significantly reduced by using gas chromatography-mass spectrometric (GC-MS) techniques. Individual dinitrophenylhydrazones were readily separated by GC and detected by both positive and negative ion MS. The two major ions in negative ion spectra were the 182 m/z fragment ion and the molecular ion. Positive ion spectra showed strong ions corresponding to the protonated molecular ion and a protonated iminium ion. The greatest sensitivity was obtained with negative ion detection (10 pg per injection). However, more structural information was obtained from analysis of the positive ion spectra. Dinitrophenylhydrazones of hydroxyaldehydes, like 4-hydroxynonenal, were analyzed after converting the dinitrophenylhydrazones into trimethylsiloxylethers. GC-MS with negative ion detection was used to identify and quantitate the release of 4-hydroxynonenal by alveolar macrophages exposed to nitrogen dioxide.

In vivo growth hormone treatment rapidly stimulates the tyrosine phosphorylation and activation of Stat3

The mechanisms by which GH regulates gene expression to alter growth and metabolism are unknown. We have demonstrated previously that in vivo GH treatment rapidly stimulates the tyrosine phosphorylation of multiple nuclear proteins and have identified the inducible transcription factor Stat1 (formerly Stat91) as one of the major GH-activated nuclear phosphoproteins. We now show that Stat3, a new member of the STAT (signal transducer and activator of transcription) family of transcription factors, is also phosphorylated on tyrosine residues and rapidly appears in the nucleus in response to GH. Activated Stat3 interacts with the naturally occurring c-sis-inducible element of the c-fos gene after GH treatment, as demonstrated by gel mobility shift assay, and is a component of gel-shifted bands A and B when the high affinity sis-inducible element is used as a probe. Our results suggest that multiple STAT proteins may mediate some of the pleiotropic effects of GH on gene expression.

Characterization of deoxyribonucleic acid-protein interactions at a growth hormone-inducible nuclease hypersensitive site in the rat insulin-like growth factor-I gene

Many of the growth-promoting effects of GH are mediated by insulin-like growth factor-I (IGF-I), a highly conserved, 70-residue basic peptide. Previous studies have demonstrated that GH rapidly stimulates IGF-I expression in vivo, and our laboratory has identified a GH-regulated alteration in chromatin configuration, manifested as a hormonally induced deoxyribonuclease-I (DNase-I)-hypersensitive site in the second IGF-I intron. In the current study, we have used in vivo DNase-I footprinting to map this hormonally responsive chromatin domain to an approximately 350-nucleotide region and have identified DNA-protein interactions within the hypersensitive site by in vitro gel mobility shift experiments and DNase-I footprinting studies. DNA-protein binding was localized to two adjacent segments of 32 and 48 nucleotides. In 1 of these regions, protein-DNA contacts were also detected in vivo on guanine residues by dimethylsulfate footprinting. DNA-binding activity was present in GH-deficient rats, but was not modified by hormone treatment. Our results define a rapid and reversible genomic alteration in response to GH in a GH-regulated gene and delineate a target within chromatin for GH action.

The role of free radicals and antioxidants: how do we know that they are working?

This review briefly discusses how free radicals are formed and the possible participation of free radicals in disease. The review describes the basic radical reactions and the types of products that are formed from the free-radical reactions of cellular constituents. In many cases, in vivo free-radical oxidation can be detected by measuring products that were derived from radical reactions. Since aerobic organisms generate oxygen-containing free radicals during oxygen metabolism, they carry chemicals and enzymes that reduce the threat posed by these radicals. The more common sources of in vivo free radicals are described in the article as well as the methods used by cells to protect themselves from free-radical damage. Generation of free radicals in vivo also may be the result of exposure to certain chemical agents present in the environment. Many of these agents cause pathologic changes to the exposed tissues and organs by initiating free-radical reactions.

Growth hormone rapidly activates rat serine protease inhibitor 2.1 gene transcription and induces a DNA-binding activity distinct from those of Stat1, -3, and -4

Transcriptional regulation by growth hormone (GH) represents the culmination of signal transduction pathways that are initiated by the cell surface GH receptor and are targeted to the nucleus. Recent studies have demonstrated that the activated GH receptor can stimulate Stat1, a cytoplasmic transcription factor that becomes tyrosine phosphorylated and translocates to the nucleus, where it can interact with specific DNA sequences to modulate gene expression. GH also has been found to induce protein binding to a portion of the rat serine protease inhibitor (Spi) 2.1 gene promoter that is required for GH-induced transcription of Spi 2.1. Using GH-deficient hypophysectomized rats as a model, we show that GH treatment rapidly and potently induces both nuclear Spi 2.1 mRNA expression in the liver and specific nuclear protein binding to a 45-bp segment of the Spi 2.1 gene promoter. A GH-inducible gel-shifted complex appears within 15 min of systemic hormone administration and can be inhibited by an antiphosphotyrosine monoclonal antibody but is not blocked by a polyclonal antiserum to Stat1, Stat3, or Stat4, even though the nucleotide sequence contains two gamma interferon-activated sequence-like elements that could interact with STAT proteins. By Southwestern (DNA-protein) blot analysis, approximately 41- and 35-kDa GH-inducible proteins were detected in hepatic nuclear extracts with the Spi 2.1 DNA probe. Thus, a GH-activated signaling pathway stimulates Spi 2.1 gene expression through a unique mechanism that does not appear to involve known members of the STAT family of transcription factors.

Chemical and biological characterization of oxo-eicosatetraenoic acids

Eicosatetraenoates (ETEs) with 5-oxo residues are known to induce human neutrophil (PMN) Ca2+ transients and chemotaxis. We find that 5-oxoETE, 5-oxo-8-trans-ETE, 5-oxo-15-hydroxy-ETE, 5-hydroxy-ETE, 5-hydroxy-15-oxoETE, 5,15-dioxoETE, and 5,15-dihydroxy-ETE have respective relative potencies of 10, 5, 3, 1, 0.2, 0.1, and 0.02 in: a) causing PMN to mobilize Ca2+, aggregate, and release small amounts of granule enzymes and b) promoting large degranulation and oxidative burst responses in PMN co-challenged with platelet-activating factor, tumor necrosis factor-alpha, or ATP. Contrastingly, 12(R)-hydroxy-ETE, 12(S)-hydroxy-ETE, and 12-oxoETE induced PMN Ca2+ transients and aggregation [respective potencies (5-hydroxy-ETE = 1) of 0.1, 0.01, and 0.003] but did not effect degranulation, and 15-hydroxy-ETE, 15-oxoETE, and 15-oxo-11-trans-ETE were inactive in all assays. Finally, 5-oxo/hydroxy-ETEs desensitized PMN to themselves but not to 12-oxo/hydroxy-ETEs or leukotriene (LT)B4; 12-oxo/hydroxy-ETEs and LTB4 desensitized PMN to themselves and each other but not to 5-oxo/hydroxy-ETEs; 15-oxo/hydroxy-ETEs did not desensitize PMN; and a LTB4 receptor antagonist blocked responses to LTB4 and 12-oxo/hydroxy-ETEs but not to 5-oxo/hydroxy-ETEs. Thus, 5-oxo/hydroxy-ETEs act by a common, LTB4 receptor-independent mechanism that recognizes 5- but not 12- or 15-oxo/hydroxy-ETEs and prefers oxo over hydroxy residues at C5 whereas 12-oxo/hydroxy-ETEs act via a LTB4 receptor mechanism that recognizes 12- but not 5- or 15-oxo/hydroxy-ETEs and prefers hydroxy over oxo residues at C12.